Heartbeating in IPA has used select.poll() for years to workaround
a bug where changing the time in the ramdisk could cause heartbeats
to stop and never resume.
Now that IPA syncs time at start and exit, this workaround is no
longer needed. So instead, we'll revert to using threading.Event()
in order to make the code simpler and easier to understand.
Since we need this to be an eventlet-event, and not a standard-thread
event, also monkey_patch threading.
Additionally, there were a few completely unused backoff interval
values set, that were never applied. In respect of maintaining the
5+ years old behavior of not doing error backoffs, that code was
removed instead of being made to work.
Change-Id: Ibcde99de64bb7e95d5df63a42a4ca4999f0c4c9b
a01646f56b