Fix Subscription's queue_name variable being tuple
Fix Subscription's queue_name variable being tuple

Because of nasty comma in the end of line of the queue_name string
variable definition, queue_name becomes a tuple with string inside,
which is wrong.

This patch fixes the problem by removing the comma.

Change-Id: Id580dfda84e4f0cb151343031d2a72ed8ef08c56
Closes-Bug: 1538367

openstack/python-zaqarclient