engine: Update pending counters in two ommited cases

The code missed two code paths that resulted in a VM being scheduled
with no update to the pending counters.

- no or empty cluster policy
- preselected host (scheduling only verified the contraints)

Change-Id: I750dadcca53e402a91bd8b36e68ee730fe177278
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1062996
Signed-off-by: Martin Sivak <msivak@redhat.com>