Idle maintenance scheduling broken.

1. The scheduling was relying on receiving battery level broadcasts
   which however are not sent if the device is asleep. The maintenance
   window was not bound and we could miss a frame if the user did
   not interact the device longer than the min time between two
   maintenance windows.

2. Hide the idle maintenance intents since this will be rewritten
   to user services.

bug:8688454

Change-Id: I17b421b09823cb46ec218cabda19e02432d94f8c