winbind: call lp_winbind_enum_{users,groups}() already in set{pw,gr}ent()

winbind: call lp_winbind_enum_{users,groups}() already in set{pw,gr}ent()

This way we don't keep winbindd_cli_state->{pw,gr}ent_state arround forever,
if the client forgets an explicit end{pw,gr}ent().

This allows client_is_idle() return true in more cases.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13293

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Volker Lendecke <vl@samba.org>