ktest: Still do reboot even for REBOOT_TYPE = script

The REBOOT_TYPE may be either grub or script, if it is script
it is expected that a REBOOT_SCRIPT is defined.

With the SWITCH_TO_TEST which is the complement of SWITCH_TO_GOOD,
which does basically the same thing as REBOOT_SCRIPT and but for
both grub and script, the REBOOT_SCRIPT does not need to be mandatory
anymore.

Do not require the REBOOT_SCRIPT and always run the reboot code
for both grub and script.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>