Make SipService listen to WIFI state change events.

+ Grab a WIFI lock if any account is opened to receive calls and WIFI is enabled
+ Release the WIFI lock if no account is opened to receive calls or WIFI is
  disabled
+ Remove screen on/off event receiver

http://b/issue?id=3077454

Change-Id: Ifdf60a850bcf4106c75ec1e7563b26d8b33d7e92
1 file changed