BugLink: https://bugs.launchpad.net/bugs/1730660

When stopping CPUS fail when doing kdump, the system will hang
indefinitively, instead of rebooting. Using the default value of 10 for
PANIC_TIMEOUT that we had for trusty allows the system to reboot.
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin King <colin.king@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>