PowerManagerService: Don't reboot directly.

Instead of calling the reboot system call ourselves, send
a message to init asking it to reboot the system. Init is in
a better position to make sure the system is cleanly shutdown.

Get rid of CAP_SYS_BOOT from system_server.

Bug: 8646621
Change-Id: I200722412844ad8d99e35a442021c6263c3ebc05
4 files changed