cntl: Change newer ctls to accept int rather than enum

Enum types in C do not have a fixed underlying type; thus if we add new
values to the enum we risk potentially breaking ABI. Additionally,
accepting int allows more flexibility when dynamically wrapping ctl
operations like some SDKs do.

Change-Id: I9b52d97aab22ab76af4ab0d4cb4acb9ece48b793
Reviewed-on: http://review.couchbase.org/39453
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>