Rework Storwize/SVC protocol to fix add_vdisk_copy

Rework Storwize/SVC protocol to fix add_vdisk_copy

Reworking some of the Storwize helper logic so that "protocol"
no longer needs to be passed around to helper functions. The protocol
being used is validated against the storage device's supported protocols
just once now, during check_for_setup_error. Also, now that the drivers
have been split, we don't need to look at the QoS' protocol key because
this is handled by the scheduler to see which drivers support given
protocols.

Change-Id: Ib331fd32b00a28115c44e7c3e4e3e998c5d9b80b
Closes-Bug: #1535921