Add logic to stop repair scripts

When watchdog detects that repair script(s) have been killed, get
a list of scripts to nuke and pass to stop_repair_scripts. Then,
get its routing key(s), and send a message from a special user to
any queue listening on those keys.

Modified an example repair script to show how it could be killed,
but need a more concrete way that that. For now, messages from
'react_killer' will raise the RepairStoppedException, which will
stop react scripts

Modified the example engine cfg to have some details about the
kombu connection to use.

Implements blueprint kill-repair-scripts
Change-Id: I67e15e9b9ebb5d36c5cb0e01995bc95f7a73b3dd