Remove explicit dependency on amqplib

amqp (or amqplib) is only accessed via kombu, and kombu
already specifies the right dependency (either amqp if new
enough or amqplib for old versions of kombu).

Change-Id: I57ad9488f196f6aec6e62fa76fae8f01f4a98216
Merge "Remove explicit dependency on amqplib"