Qpid: advance thru the list of brokers on reconnect

In Qpid implementation, when using multiple qpid_hosts, we don't want to
immediately retry failed connection for the same failed broker. This was not
the case in existing implementation though, where we've always attempted to
reconnect starting from the first broker in the list of candidates. So if the
first broker failed, we initiated reconnect to the same failed broker.

This change makes reconnect() implementation to select the next broker in the
list. This also means that non-failure reconnect attempts will also switch the
current broker. All in all, users should not rely on any particular order to
use brokers from the list, so this should not constitute an issue.

This is a backport of the following changes from oslo.messaging:
* I257c2ad6d7ebead356c0239134340975da6dbc07 (code change)
* I32e20c0e747e6489dab4b0358d422b8a9c6b982e (unit test).

Change-Id: Ia148baa6e1ec632789ac3621c85173c2c16f3918
Partial-Bug: 1261631
(cherry picked from commit 7fe95de20ccdfa5aa523ccb8a9ca3afdde5eddbb)
RabbitMQ: advance thru the list of brokers on reconnect

In RabbitMQ implementation, when using multiple rabbit_hosts, we don't want to
immediately retry failed connection for the same failed broker. This was not
the case in existing implementation though, where we've always attempted to
reconnect starting from the first broker in the list of candidates. So if the
first broker failed, we initiated reconnect to the same failed broker.

This change makes reconnect() implementation to select the next broker in the
list. This also means that non-failure reconnect attempts will also switch the
current broker. All in all, users should not rely on any particular order to
use brokers from the list, so this should not constitute an issue.

This is a backport of 71c6866471d628b207d7c5b84bfd37cc9fed0898 from
oslo.messaging.

Change-Id: I67923cb024bbd143edc8edccf35b9b400df31eb3
Partial-Bug: 1261631
(cherry picked from commit abe3e5ee994fddd5141e2cae3f4785ffe62805ea)
Merge "Qpid: advance thru the list of brokers on reconnect" into stable/havana