Bump kombu requirements

Now that we require msgpack, old version of kombu are not compatible
with msgpack<0.2 and breaks. So let's depend on versions of kombu that
supports msgpack>=0.2.

Fixes: bug 1134575

Change-Id: I910ff21f3df75e486816aea533396852eb3fbf16
Signed-off-by: Julien Danjou <julien@danjou.info>
Merge "Bump kombu requirements"