Add check credentials to log message if rabbmitmq closes socket

If one has the credentials misconfigured for rabbitmq currently the following
error message is shown: "AMQP server on 10.0.0.23:5672 is unreachable:
Socket closed. Trying again in 1 seconds. " This is confusing because the
problem is the login creditentials are wrong but the server can be reached.

Since the rabbmitmq server allowed the initial connection and closed the
socket it's likely an authenication issue. This patch now logs: "AMQP server
10.0.0.23:5672 closed the connection. Check login credentials: Socket closed"
to hint the user that it could be a credential issue.

Change-Id: Iadff35d88a9cf704c1edd2d5036a113966db3ea3
Closes-bug: 1325750
(cherry picked from commit bf281aace507dec7547e40f68d8cd7bb290dc903)
Merge "Add check credentials to log message if rabbmitmq closes socket" into stable/icehouse