relax amqplib and kombu version requirements

as nova did while ago.

this particular version of kombu doesn't work if newer msgpack happens
to be installed on the system.

bug 1178512

Change-Id: I2749623036723b5a772b1c4c01dc07437e421925
(cherry picked from commit 3a50a702f94344ef9903d1c7342d7d516e44a254)
Merge "relax amqplib and kombu version requirements" into stable/grizzly