ktest: Reboot to good kernel after every bisect run

Reboot after each bisect run regardless if the bisect passed
or failed. The test may just be to boot the kernel and that kernel
may not have a way to copy the next kerne to it. Reboot to a known
good kernel after each bisect run.

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