Fixes Opt types in glance/notifier/notify_kombu.py

Changed rabbit_retry_backoff and rabbit_retry_max_backoff to IntOpt.

Fixes bug #1201697

Change-Id: Ia1a74b6bb2873e59677a7fea6652a6c006f38175
(cherry picked from commit c1d7b5929db0e66539e4ba3cdf91a41547fd7f49)