Set Settings.Global.WIFI_SCAN_ALWAYS_AVAILABLE default value

To be able to customize the "WiFi scan always available"
setting we need to set a default value.

Change-Id: I3673f2613ab9b6a947aed7e29d4cc876140c2180
Merge "Set Settings.Global.WIFI_SCAN_ALWAYS_AVAILABLE default value" into cm-11.0