Ceph

Teuthology (the suite in particular) should be able to merge bits of yaml together. For instance, we should be able to say:

Run the suite, with these additional options:

kernel:
   client:
     branch: wip-kernel-thing
 ceph:
   branch: wip-mds-thing

or whatever, and have those options supplement (or add entirely new) sections to the run as needed.

Obviously we can't merge arbitrary yaml together.. if there is some problem (items exist with different types) we can throw an exception.