Remove explicit dependency on amqplib

kombu already depends on amqp or amqplib depending on its
version, and no explicit access to amqplib exists in neutron code.

Conflicts:
	requirements.txt

Closes-Bug: #1317094
Change-Id: I5cf189d7173b732cba6df3f9b6aff1d2bb85cdfe
(cherry picked from commit 39ffcb0dd75d9dc5d8a249f2974a67f0def5204b)
Merge "Remove explicit dependency on amqplib" into stable/icehouse