Fix issue #27653326: Sync doesn't work in doze maintenance

Add a (configurable) delay between when we start a maintenance
window until the minimum time we will end it.

Also switch to using the alarm manager callback API.  (Yay!)

Also fix a little printing problem in the alarm manager dump
so we put the package name and not some class hash in the
summary string of an alarm entry.

Change-Id: I4281e5c80bc8b26ebc1fb6f603ec33ec0e379daa