Allow use of oslo.messaging 1.3.0a4 from pypi

In I87eaefb37fa52142d47b4aba4f3f76452771f74e we are having beta
releases of oslo.messaging be uploaded to pypi.

We need to do this because of reported change in behaviour in pip
1.5 - from sdague:

  pip 1.5 disables non pypi urls by default, all of them will need
  to be explicitly white listed.

Change-Id: I94843886ef0b40670fb82733048113c9ef7c3c46
Merge "Allow use of oslo.messaging 1.3.0a4 from pypi"