Update glance::notify::rabbitmq options

This patch is aim to update rabbitmq options in notify::rabbitmq
class to keep consistent with glance-api.conf. And fix description
error in comment.

Fixes bug #1221008

Change-Id: I441a61bb683552e1696f779c733db561cca03b64
(cherry picked from commit e2fef179c13faf0a4ac6d1a512701cb873ede355)
Merge "Update glance::notify::rabbitmq options" into stable/grizzly