Configure TCP keepalive setting to all nodes

In some cases, it has been observed that services keep their
connection to RabbitMQ when they should not (e.g. during a
controller server hard reboot), creating instability. This patch
aims at fixing this by setting TCP keepalive parameters for
RabbitMQ connections, and setting kernel parameters to send
keepalive packets more often.

Change-Id: I7688a86e4ff617f20d6767f156c5d880e0d4d619
Fixes: bz#1167414
(cherry picked from commit 86a166a4718ae90eab78949f82f4f7c12ded2a6c)
Merge "Configure TCP keepalive setting to all nodes" into juno