Update ensure()/reconnect() to catch MessagingError

The error handling code that gets connections reset if necessary
caught ConnectionError. It really needs to catch MessagingError,
which ConnectionError inherits from. There are other types of
MessagingErrors that may occur, such as InternalError, and they need
to cause the connection to reset, as well.

This fix has already been merged into oslo.messaging.

--

Cherry-picked from oslo-incubator 234f64d608266f43d8856ff98c89ceba6699d752
See also https://bugzilla.redhat.com/show_bug.cgi?id=1086077

Closes-bug: #1303890
Change-Id: Ic5082b74a362ded8b35cbc75cf178fe6e0db62d0
Set python hash seed to 0 in tox.ini

New tox (>=1.7.0) sets a random python hash seed by default. This is
generally good for testing because it will help keep projects working
regardless of the hash seed, but ceilometer unittests don't currently
pass with a random hash seed so set it to the python default seed.

This change will allow us to use new tox again and remove the
restriction on tox<=1.6.1 to run unittests.

Redundant setenvs for specific test envs are removed to prevent them
from overriding the PYTHONHASHSEED value.

Note this change will need to be backported to the stable branches to
keep unittests there working with new tox as well.

Conflicts:
	tox.ini

Change-Id: Ibc613d77ad52d5f7d8d613f3dd66ffba4117ff72
(cherry picked from commit 860a2852ca92df20fa886cec2e75d753ac6e18bb)
Merge "Update ensure()/reconnect() to catch MessagingError" into stable/havana
Merge "Set python hash seed to 0 in tox.ini" into stable/havana