[1159003] Alert notification sending fails due to database deadlock error
Remove the umbrella Tx surrounding sending of alert notifications.  It used
to be that all notifications would be sent in one REQUIRES_NEW SLSB call. It
was necessary to do this because the notifications were themselves sent
within a larger, very heavy, umbrella Tx that involved the alert generation
itself (among other things). Prior work restructured that logic and
moved notification sending to a more logical place, executing after
alert generation, cache update and recovery logic handling.  But the prior
work left the notification sending under a single transaction.  This
isn't really necessary or desirable. Each notification should be processed
individually, not holding any resources past its execution, and
persisting each notification log in its own Tx.  Although not proven,
the deadlock situation was likely caused when an alert definition defined
multiple notifications, and one held resources required by another.

Also, rename some local SLSB methods with "Tx" suffixes to better reflect
their behavior.
[BZ 1158892] Remove AllEndpointStates property of FailureDetector service from the plugin descriptor. This will prevent a high curn of configuration changes for the service due to the ever changing nature of the property. The property is not needed at this point by any functionality in the Cassandra or Storage Node plugins.
Bug 1139189 - If a server is in 'MAINTENANCE' mode, should be indicated to
user on login

Now we display sticky warning in case mainenance mode is detected after
login. This does not add a check for server mode to every request, just the
first request after login - this is when we build CoreGui