schedule_suite.sh: ensure ceph and kernel branches exist

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 0c663ca84e75751eb930016516e1b18cee37acdb)
schedule_suite.sh: take option teuthology branch arg

Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 7309bccca300743ecb9874dc3f69648d36b4fc8d)