This is not a change in behavior, but a change in when / whether
we notify the user that we aren't doing scheduled backups while in
power saver mode.

This is an attempt to balance two considerations:
- Usersvwill care more about power saver mode in the short term than
  an automatic backup. They know if they have an uncharged laptop,
  etc.
- But over time (and especially if they accidentally left their
  device on manual power saver mode), we should at least warn them
  that we are not backing up while in this mode, and thus give them
  a chance to correct that.

I'm going with the theory that a day delay is appropriate. Let's
see how users find that balance.