handle KeyboardInterrupt

When running zuul in non-daemon mode (with -d), it is often useful to
abort it using Control + C.

Change-Id: I385a41625633f3120b95c07283bef015824e5853
Reviewed-on: https://review.openstack.org/13571
Reviewed-by: Monty Taylor <mordred@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins
1 file changed