linux: Re-poll batteries after a line power change

When a change on a line power occurs, then re-poll all batteries aggressively for a while. It is very common for batteries to take about a second to refresh their state and many will not send appropriate notifications in this case.

Closes: #179 (closed), #159 (closed)

@hadess, I think you have a macbook. Do you think we can drop the up_backend_needs_poll_after_uevent test with this? Are you maybe able to test this?