LiveMerge: Remove old merge APIs

The old merge and mergeStatus APIs were never adopted and in order to
make way for the new live merge feature let's remove this dead code
first.

Change-Id: I33c4d01e17cf5d2362df25f0ab104a42a485e14f
Signed-off-by: Adam Litke <alitke@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/26632
Reviewed-by: Federico Simoncelli <fsimonce@redhat.com>