uas: zap_pending: data urbs should have completed at this time

The data urbs are all killed before calling zap_pending, and their completion
handler should have cleared their inflight flag.

Do not 0 the data inflight flags, and add a check for try_complete succeeding,
as it should always succeed when called from zap_pending.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>