Fixing glance-api hangs in the qpid notifier

Glance-api was able to hang in qpid notifier under heavy image creation load.

The ``thread`` and ``select`` modules used by the python-qpid for managing
the AMQP connection. When the eventlet was not able to switch between threads
because leaded to hang and/or pipe(2) leaking issues.

* Monkey patching the ``select`` and ``thread`` modules to be  eventlet friendly
  in order to avoid hanging issues.

* The reference to the connection object in the QpidStrategy
  was replaceable by a concurrent thread, which could cause various issues.
  Using just local variables for storing connection object in order to avoid
  concurrent unsafe manipulation.

Fixing bug 1229042

Change-Id: I8fa8c4f36892b96d406216cb3c64854a94ca9df7
(cherry picked from commit 2e7aa761b6c2b31f4cbd9703ee19090b6757508a)