Passing a filter expression and selecting an address family using the
'-f' flag would overwrite the state filter by accident. Therefore
calling e.g. 'ss -nl -f inet '(sport = :22)' would not only print
listening sockets (as requested by '-l' flag) but connected ones, as
well.

Fix this by reusing the formerly ineffective call to filter_states_set()
to restore the state filter as it was before the call to
filter_af_set().
Signed-off-by: Phil Sutter <phil@nwl.cc>