Remove unused notifier and rpc modules from oslo sync

As part of the move to oslo.messaging (1a91aacb85922f8d74733979691f0bf26249debc)
we stopped using oslo-incubator's notifier and rpc, but openstack-common.conf
wasn't updated accordingly.

Change-Id: I11e17313afa0327ba4620dd8f08ecf379efef9ac
Merge "Remove unused notifier and rpc modules from oslo sync"