Fix client connection leaks in HP3PAR drivers

In the presence of exceptions, hp3parclient connections
did not get closed. This fix adds try/finally blocks
around all client login/logout calls.

Change-Id: I105b06cea5e61f3e9cf0d6e19c7ce430fedad715
Closes-Bug: 1220948
Merge "Fix client connection leaks in HP3PAR drivers"