Implement registration retry mechanism in failure cases, REF 14471

cherry-pick the following changes from devel
- When SIP response 408/503/500 is received for SIP Register requests
  to all server addresses, the failover retry will be scheduled
  with certain time interval.
- If number of continuous failed retries reached 'failover_max_retries',
  the SIP registraion will be given up. By default, the number is '-1',
  i.e. unlimited.
- 'failover_interval1' is used between normal failover retries, which
  is 10 seconds by default.
- 'failover_interval2' is used once after every 3 continuous retries,
  which is 60 seconds by default.

More timer (T1,T2,T4,TD/TB) configuration added from asterisk to pjsip.

Priority after this changes:
* retry_after (if received, as above diagram)
* failover_max_retries (if have non-zero values, -1 as infinitive)
* retry_interval (if set, default 1 if not set)
* above diagram base on RFC