fixup: include cntl.h

Change-Id: I92200eb0d0e5abc6786bc5e4234b1ea2592031d9
Reviewed-on: http://review.couchbase.org/27923
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>