SIP TCP transport client not being reused on MacOS platforms (thanks Emil Sturniolo for the report)

[nanang]

Seems that this is caused by transport manager failure in looking up existing transport in transport hash table. As the the sockaddr (address of remote target) is used as the key in transport hash table, any inconsistencies in sockaddr structure may cause PJSIP to fail to find matching transport.

Found that some new APIs don't set sin_len member of sockaddr to zero. By convention, this sin_len member must be set to zero by PJLIB.

This symptom may also occur on any platforms that has sin_len member in sockaddr, e.g: BSD family.

[nanang]

In r3044:

• Fixed bug in some APIs of address resolver and IP helper to reset sin_len member of sockaddr.
• Added purity test of sin_len member checking in PJLIB unit test (pjlib_test).
• Fixed bug in pj_getaddrinfo() when address family param set to PJ_AF_UNSPEC (assertion raised as it called pj_sockaddr_get_addr() with PJ_AF_UNSPEC too).