cbc: allow `pillowfight` as pseudo-subcommand

Some users are familiar with the older form of `cbc pillowfight`. Let's
allow this use case if possible.

Change-Id: I5c496d59e1cc09567449d1d77380a1bc99aee502
Reviewed-on: http://review.couchbase.org/40189
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>