The command will now default to the image currently in-use by the server, effectively making the --image parameter optional. This commit also adds basic tests for ServerRebuild since there wasn't any. Will add more full tests for it. Change-Id: I733fd3ad5a825f06563c72aa430122e1a0e3b3b0 Closes-bug: #1524406 Co-Authored-By: David Moreau Simard <dms@redhat.com> Co-Authored-By: Tang Chen <tangchen@cn.fujitsu.com>