(POOLER-26) Fix lost VMs getting stuck in pending

This commit updates vmpooler to understand how to resolve a situation
where a pending VM does not exist. Without this change a pending VM that
does not exist in vmware inventory gets stuck in the pending state,
preventing the pool from ever reaching its target capacity.

As a part of this change the find_vm method is updated to perform a
light, then heavy search each time find_vm is called and all usage of
find_vm || find_vm_heavy is replaced. This makes find_vm usage
consistent across pool_manager.

Additionally, open_socket method is updated to resolve an incorrect
reference to the host name.

spec/vmpooler/pool_manager_spec.rb

@@ -26,7 +26,6 @@ describe 'Pool Manager' do
       it 'calls fail_pending_vm' do
         allow(vsphere).to receive(:find_vm).and_return(nil)
         allow(redis).to receive(:hget)
-        expect(redis).to receive(:hget).with(String, 'clone').once
         subject._check_pending_vm(vm, pool, timeout, vsphere)
       end
     end