Disable retry on cleanup logout

It may occur that the exit logout could get hung
up for one reason or another. Change to opportunistically
trying to logout.

It would have to fail generally around 3 times within a minute
for it to be a problem, so it is unlikely to ever
be a problem should it fail.

Change-Id: Ie32b2ae03618fe078e3965d9ee68dda962206bfe

pyghmi/ipmi/private/session.py

@@ -321,7 +321,7 @@ class Session(object):
             for portent in list(cls.bmc_handlers[sesskey]):
                 session = cls.bmc_handlers[sesskey][portent]
                 session.cleaningup = True
-                session.logout()
+                session.logout(False)
 
     @classmethod
     def _assignsocket(cls, server=None, forbiddensockets=()):