SIP: fixing SipServiceImpl

+ synchronize on the service instance across all objects to avoid deadlock
+ use SystemClock.elapsedRealtime() instead of System.currentTimeMillis()
+ grab wifi lock when wifi is on *and* at least one SIP account is registered
  and release wifi lock if no SIP account is registered even when wifi is on.
+ handle network connectivity exception better
+ call back even when the auto registration process is stopped

Change-Id: I5180828861b4f468d7c6f4f0d113bb27d65ec48c
2 files changed