res_pjsip_sdp_rtp: Fix setting of address type for rtp_ipv6

create_outgoing_sdp_stream was setting "addr_type = STR_IP6" only
when an ipv6 media_address was specified on the endpoint.  If
rtp_ipv6 was set and ast_sip_get_host_ip_string returned an ipv6
address, we were leaving the addr_type set at the default of
STR_IP4.  This caused the address type to be set incorrectly on the
"o" and "c" SDP attributes even though the address was set
correctly.  Some clients don't like the mismatch.

 * Removed the test for endpoint/media_address and now check all
   addresses for ipv6.

ASTERISK-27198
Reported by: Martin Cisárik

Change-Id: I5214fc31b728117842243807e7927a319cf77592