If there are local services running on an interface that sits on top of bat0
these interfaces may be added to the translocal batman-table. Contrary
to the bat0-interface itself this entries are not marked with the
TT_CLIENT_NOPURGE -flag and are thus added to the client-count reported by
respondd. In this case the client-count reported is one too high.

This change adds an additional check to the function doing the actual
counting. This check makes sure that no local interface is counted as a
client.

Since respondd only collects data in an interval of minutes (depending
on the site's configuration) the additional costs for this check should
be negligible.