inputselector: Always proxy position/duration query

inputselector: Always proxy position/duration query

active-pad switch causes reconfigure event with lock taken,
and upstream element might query the current position or duration
before returning the reconfigure event.
Meanwhile, gst_input_selector_get_linked_pad() is used to get srcpad
inside of default query handle, and it takes also lock.
Since inputselector is still locked by active-pad switch, and so the query
cannot be handled further.

https://bugzilla.gnome.org/show_bug.cgi?id=775445