(POOLER-52) Modify dummy provider to use a connection pool

Previously a connection pooler class was added.  This commit modifies the Dummy
VM Provider to use a connection pooler.  While the Dummy provider strictly
speaking does not use connections, this allows testing to see what happens when
connection pools are stressed or exhausted.  This commit:
- Modifies functions to use a connection pool object for the public API
  functions
- Modifies the VMPooler YAML with new settings for connection pool size and
  timeout

spec/unit/providers/dummy_spec.rb

@@ -76,11 +76,11 @@ describe 'Vmpooler::PoolManager::Provider::Dummy' do
   let(:config) { YAML.load(<<-EOT
 ---
 :config:
-  max_tries: 3
-  retry_factor: 10
 :providers:
   :dummy:
     key1: 'value1'
+    # Drop the connection pool timeout way down for spec tests so they fail fast
+    connection_pool_timeout: 1
 :pools:
   - name: '#{pool_name}'
     size: 5