(POOLER-107) Add configuration API endpoint

This commit adds a configuration endpoint to the vmpooler API. Pool
size, and pool template, can be adjusted for pools that are configured
at vmpooler application start time. Pool template changes trigger a pool
refresh, and the new template has delta disks created automatically by
vmpooler.

Additionally, the capability to create template delta disks is added to
the vsphere provider, and this is implemented to ensure that templates
have delta disks created at application start time.

The mechanism used to find template VM objects is simplified to make the flow of logic easier to understand. As an additional benefit, performance of this lookup is improved by using FindByInventoryPath.

spec/unit/providers/vsphere_spec.rb

@@ -283,6 +283,7 @@ EOT
 
     let(:clone_vm_task) { mock_RbVmomi_VIM_Task() }
     let(:new_vm_object)  { mock_RbVmomi_VIM_VirtualMachine({ :name => vmname }) }
+    let(:new_template_object)  { mock_RbVmomi_VIM_VirtualMachine({ :name => vmname }) }
 
     before(:each) do
       allow(subject).to receive(:connect_to_vsphere).and_return(connection)
@@ -305,19 +306,10 @@ EOT
       end
     end
 
-    context 'Given a template path that does not exist' do
-      before(:each) do
-        config[:pools][0]['template'] = 'missing_Templates/pool1'
-      end
-
-      it 'should raise an error' do
-        expect{ subject.create_vm(poolname, vmname) }.to raise_error(/specifies a template folder of .+ which does not exist/)
-      end
-    end
-
     context 'Given a template VM that does not exist' do
       before(:each) do
         config[:pools][0]['template'] = 'Templates/missing_template'
+        expect(subject).to receive(:find_template_vm).and_raise("specifies a template VM of #{vmname} which does not exist")
       end
 
       it 'should raise an error' do
@@ -327,7 +319,8 @@ EOT
 
     context 'Given a successful creation' do
       before(:each) do
-        template_vm = subject.find_folder('Templates',connection,datacenter_name).find('pool1')
+        template_vm = new_template_object
+        allow(subject).to receive(:find_template_vm).and_return(new_template_object)
         allow(template_vm).to receive(:CloneVM_Task).and_return(clone_vm_task)
         allow(clone_vm_task).to receive(:wait_for_completion).and_return(new_vm_object)
       end
@@ -339,7 +332,7 @@ EOT
       end
 
       it 'should use the appropriate Create_VM spec' do
-        template_vm = subject.find_folder('Templates',connection,datacenter_name).find('pool1')
+        template_vm = new_template_object
         expect(template_vm).to receive(:CloneVM_Task)
           .with(create_vm_spec(vmname,'pool1','datastore0'))
           .and_return(clone_vm_task)
@@ -3578,5 +3571,52 @@ EOT
     end
   end
 
+  describe 'find_template_vm' do
+    let(:vm_object) { mock_RbVmomi_VIM_VirtualMachine() }
 
+    before(:each) do
+      allow(connection.searchIndex).to receive(:FindByInventoryPath)
+    end
+    it 'should raise an error when the datacenter cannot be found' do
+      config[:providers][:vsphere]['datacenter'] = nil
+
+      expect{ subject.find_template_vm(config[:pools][0],connection) }.to raise_error('cannot find datacenter')
+    end
+
+    it 'should raise an error when the template specified cannot be found' do
+      expect(connection.searchIndex).to receive(:FindByInventoryPath).and_return(nil)
+
+      expect{ subject.find_template_vm(config[:pools][0],connection) }.to raise_error("Pool #{poolname} specifies a template VM of #{config[:pools][0]['template']} which does not exist for the provider vsphere")
+    end
+
+    it 'should return the vm object' do
+      expect(connection.searchIndex).to receive(:FindByInventoryPath).and_return(vm_object)
+
+      subject.find_template_vm(config[:pools][0],connection)
+    end
+  end
+
+  describe 'create_template_delta_disks' do
+    let(:template_object) { mock_RbVmomi_VIM_VirtualMachine({
+        :name => vmname,
+      })
+    }
+
+    before(:each) do
+      allow(subject).to receive(:connect_to_vsphere).and_return(connection)
+    end
+
+    context 'with a template VM found' do
+
+      before(:each) do
+        expect(subject).to receive(:find_template_vm).and_return(template_object)
+      end
+
+      it 'should reconfigure the VM creating delta disks' do
+        expect(template_object).to receive(:add_delta_disk_layer_on_all_disks)
+
+        subject.create_template_delta_disks(config[:pools][0])
+      end
+    end
+  end
 end