Don't use a connection pool unless provided

To prevent left over TCP connections from keystoneclient not correctly
cleaning up we shouldn't use a connection pool. This is not ideal but it
was a relatively new addition so shouldn't affect performance.

When we are able to find a long term solution to keystoneclient's other
problems we can move back to using a connection pool.

Change-Id: I45678ef89b88eea90ea04de1e3170f584b51fd8f
Closes-Bug: #1282089
Merge "Don't use a connection pool unless provided"