Cleaned up references to executor specific RPCServer types

In oslo.messaging design phase, it was planned to introduce executor
specific RPCServer types though they were never implemented. References
to those types sneaked into docstrings from the original design
document. Since we're not going to implement those types now, docstrings
should be updated accordingly.

Change-Id: Ic4017bb8f89d47115bb7dc59483e81d26c76212b
Add an example usage of RPCClient retry parameter

Change-Id: Ib88870b312721deff0d9b6db2ba2e3cb99da6038
Fix the notify method of the routing notifier

The notify method of the routing notifier don't have the correct
signature and change the case of the priority.

This change fixes it.

Change-Id: I833b19d0c054c94b861a4f6cc263c3487fa0e544
Closes-bug: #1316681
Merge "Fix the notify method of the routing notifier"
Updated from global requirements

Change-Id: I71fd4b1292d68279d75569dc022745b75da66eab
Merge "Add an example usage of RPCClient retry parameter"
Merge "Cleaned up references to executor specific RPCServer types"