Added ignore-cache and flush-cache options

- ignore-cache will ignore the cache of the specified jobs and update
  them no matter what
- flush cache will entirely flush the cache before updating, no matter
  which jobs are specified

Change-Id: I345349ccfe296a5a57360366497400a859b98b42
Signed-off-by: David Caro <dcaroest@redhat.com>
Merge "Added ignore-cache and flush-cache options"