(POOLER-184) Pool manager retry and exit on failure

Adding a reconnect retry for redis, which by default would retry 10 times,
for a total wait time of ~80 seconds

spec/unit/generic_connection_pool_spec.rb

@@ -25,6 +25,13 @@ describe 'GenericConnectionPool' do
       connection: 'connection'
     }}
 
+    it 'should error out when connection pool could not establish no nothing' do
+      newsub = Vmpooler.redis_connection_pool("foo,bar", "1234", "fuba", 1, 1, metrics, 0)
+      expect { newsub.with_metrics do |conn_pool_object|
+        conn_pool_object.srem('foo', "bar")
+      end }.to raise_error Redis::CannotConnectError
+    end
+
     it 'should return a connection object when grabbing one from the pool' do
       subject.with_metrics do |conn_pool_object|
         expect(conn_pool_object).to be(connection_object)