Bugfix: config.Strings()

will automatically prune away empty elements.

Change-Id: Ic5ac24279e5662b3b206b1f90e963c32cdd811bb
Reviewed-on: http://review.couchbase.org/43468
Reviewed-by: Sarath Lakshman <sarath@couchbase.com>
Reviewed-by: Pratap Chakravarthy <prataprc@couchbase.com>
Tested-by: Pratap Chakravarthy <prataprc@couchbase.com>