* gen_pktline() in smart_protocol.c was skipping refspecs that deleted
refs that were not advertised by the server. The new behavior is to
send a delete command with an old-id of zero, which matches the behavior
of the official git client.
* Update test_network_push__delete() in reaction to above fix.
* Obviate messy logic that handles missing push_spec rrefs by canonicalizing
push_spec. After calculate_work(), loid, roid, and rref, are filled in with
exactly what is sent to the server
