MB-10368: Stop monitoring partition db files

The monitoring of the master database (which contains the
design documents) is also removed as it isn't used elsewhere
in the code.

Change-Id: I6195a9104a9c208635de8679634e2d3b0093467d
Reviewed-on: http://review.couchbase.org/34440
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>