Fixing leaking sessions in 3PAR on attach/detach

Fixed an issue where sessions were not being closed properly
during an attach or detach of a volume.

Closes-Bug: 1367429
Change-Id: Ic7a4ceca855111a8c8a9512fc2d99fcf6df6d79e
Merge "Fixing leaking sessions in 3PAR on attach/detach"