Update oslo.messaging to 1.4.0.0a3

This oslo.messaging version fixes a problem with encoding
issue in source file(review 102909), causing some Neutron
gate test failures (e.g. 102351). Using a3, since it is the
latest.

Change-Id: I673b5d505c8b7d43d59f7516e345f92221483a51
Update oslo.config to 1.4.0.0a2

oslo.config 1.4.0.0a1 has the config fixture which Keystone can
use.

1.4.0.0a2 has the config generator which Glance and Nova will
adopt, and cfgfilter which oslo.messaging wants to adopt.

Change-Id: I6c3049e6e379c83af7e6e7df8855b1a6c0b698e7
Merge "Update oslo.messaging to 1.4.0.0a3"
Merge "Update oslo.config to 1.4.0.0a2"