Sync rpc from oslo-incubator

This includes the following changes:

76972e2 Support a new qpid topology
284b13a Raise timeout in fake RPC if no consumers found
9721129 exception: remove
7b0cb37 Don't eat callback exceptions
69abf38 requeue instead of reject

Change-Id: I58051558345cdb94a9ad29edf02acba9952f6f60
Closes-bug: #1178375
Append /usr/sbin:/sbin to the path for searching mongodb

At least on SUSE, it is not installed in /usr/bin,
which means it can not be found as normal user.

Change-Id: I636cb16429962807d9e88ba87e494ac3c7e1e5a9
Merge "Append /usr/sbin:/sbin to the path for searching mongodb"
Merge "Sync rpc from oslo-incubator"