Fixes #8317 - Implement Reboot action

> Not sure changing the progress bar will help as it might be too fast to notice if you're not staring at the screen the whole time but a notice message makes sense.

Oh sorry to be misleading. I mean - this is how it works today. I am not
sure if red color for the progress bar was related to the fact that host
was not booting,

Anyway the flash should make this more transparent. Or when @ohadlevy
thinks its better to rollback, then the problem is solved (return
false).

-- 
Later,
 Lukas #lzap Zapletal