Move cbauditd from enterprise to memcached.

By default enterprise projects should reside in the enterprise
directory.  However cbauditd needs to be in a subdirectory of
memcached because it is referenced as a link target by memcached.

Change-Id: I2dcf824ab4c7bbe697c158580c40410ba2eeefb8
Reviewed-on: http://review.couchbase.org/43848
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>