Fix performance issues with brocade zone driver.

Removed firmware checks from common path as the ssh invoke_shell
was taking 5 seconds to complete for each firmware check.
Refactored to only do cfgsave in non-activate case.
Removed extra calls to switch to get the active zoneset.

Closes-Bug: #1292119

Change-Id: Ie1c2c0c603f6dd68439f2c2db74b21ea2dd0fc11
Merge "Fix performance issues with brocade zone driver."