Terminal update and Undo leave Home stopped #509

Seen on the signed 0.8.0-alpha.26 on Linux and Jetson (#93 comments 6521408803 and the Linux acceptance comment): elastos update and elastos update --rollback-to <head CID> stop a running Home and end with "Home is stopped. Start it with: …". The running Home prints "Error: Home stopped. Start Home again." and exits; nothing restarts it. An update through System > About restarts Home by itself.

docs/INSTALL.md "Undo an update" does not say Home stops, and Undo is terminal-only, so a person who uses Undo is left with Home down until they run the printed command.

Done means (0.8.1): when Home was running before a terminal update or Undo, it is running again on the new version afterwards (or, if that is not wanted, INSTALL.md says so in the Undo and Terminal sections); an installed check covers both cases.