CoraidDriver: typo in _login exception handler

In cinder/volume/drivers/coraid.py, _login method, if login is
unsuccessful, we try to get the message from an undefined
object "response". Instead we should be getting it from "reply".

- errmsg = response.get('message', '')
+ errmsg = reply.get('message', '')

Fixes bug 1157499

Change-Id: Ifd047ced6b40f49881e81d4e73189d9bd216c903
(cherry picked from commit 4403230bbe8f39a19c38e58840bbb2283ccd808f)
Merge "CoraidDriver: typo in _login exception handler" into milestone-proposed