pjsip: restrict function PJSIP_PARSE_URI to parse only SIP/SIPS URIs

The next usage of PJSIP_PARSE_URI will crash asterisk
${PJSIP_PARSE_URI(tel:+1234567890,host)}
or
${PJSIP_PARSE_URI(192.168.1.1:5060,host)}

The function pjsip_parse_uri successfully parses then, but returns
struct pjsip_other_uri *.

This patch restricts parsing only SIP/SIPS URIs.

Change-Id: I16f255c2b86a80a67e9f9604b94b129a381dd25e