resolve KeyError for IBM Storwize/SVC driver

When using iSCSI protocol to conenct IBM v7000, and compression
is not enabled for the system, KeyError may occur because of the response
item's lack of 'license_compression_enclosures'. So add a check to
resolve it.

Change-Id: Ie53631ea5b047650897313ad5614f6e1df5377f2
Closes-Bug: #1288645
Merge "resolve KeyError for IBM Storwize/SVC driver"