res_pjsip_session: Don't restrict non-audio default streams to sendrecv.

The state of the default audio stream is used for hold/unhold so we
restrict it to sendrecv as the core does not handle when it changes as
a result of hold/unhold.

This restriction does not apply to other media types though so we now
only restrict it to audio. This allows the other default streams to
store their state at all values, and not just sendrecv and removed.

ASTERISK-28783

Change-Id: I139740f38cea7f7d92a876ec2631ef50681f6625