Give specific messages if job was killed due to SIGTERM or SIGKILL (a…

…nsible#12435)

* Reap jobs on dispatcher startup to increase clarity, replace existing reaping logic

* Exit jobs if receiving SIGTERM signal

* Fix unwanted reaping on shutdown, let subprocess close out

* Add some sanity tests for signal module

* Add a log for an unhandled dispatcher error

* Refine wording of error messages

Co-authored-by: Elijah DeLee <kdelee@redhat.com>

awx/main/management/commands/run_dispatcher.py

@@ -7,7 +7,7 @@
 from django.core.management.base import BaseCommand
 from django.db import connection as django_connection
 
-from awx.main.dispatch import get_local_queuename
+from awx.main.dispatch import get_local_queuename, reaper
 from awx.main.dispatch.control import Control
 from awx.main.dispatch.pool import AutoscalePool
 from awx.main.dispatch.worker import AWXConsumerPG, TaskWorker