Change-Id: I40b8bd6090877d189bb9990f9d3c2b6eadba03f7

Change-Id: Ia163a74b5c35a09abecaabee41af551ccb402c77

Change-Id: I04dbfb8d3b7a85d31b67f3f66044838da7745fb1

In situations where the built-in (and default) kazoo
threading async handler does not work (which sometimes
appears to happen under eventlet) allow for specifying
a different handler (ie the 'eventlet' one) that should
work better under those scenarios.

Closes-bug: #1512001
Change-Id: Iec5e39928b223a3ffca0b9b5b4d0fd61abaa0f2b
(cherry-picked from commit 9c5cb6fd0ba6b08fd163130a8862137277e48020)

Change-Id: Ic608e2495b6c7e13cf2407f3577867c2d696e617

Change-Id: Iaca842a5c18b0277791a53809f6bd44ec131720a

This change adds a test to ensure that lock acquired from different
threads/processes work as expected. And fixes drivers when they won't.

With file driver, when two threads acquire the lock, when the first one
releases it, the second get a 'ValueError: I/O operation on closed file'
because the first have closed the file after releasing the lock.
Now, the file is open when the lock object is created and we let the GC
to close it when we don't need it anymore

With mysql, postgres, kazoo driver, multiple acquire inside the same
backend session, doesn't work like a exclusive lock, so we track the
status locally when we get the lock inside a process.

Change-Id: Ic990a79c9baebe534409c1a433e21f4a2f9a7d6a
(cherry picked from commit 6bab678e6ea1a5b087a636279f2db873554a4116)