MB-7460: Don't double print watermark stats

We have these in the config so we don't need to explicitly print
them.

Change-Id: I23e25849c61c1080a850ab72a0038197c9e53aeb
Reviewed-on: http://review.couchbase.org/23667
Reviewed-by: Jin Lim <jin@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>