ktest.pl: Powercycle the box on reboot if no connection can be made

When performing a reboot of the test box, try to ssh to it. If it can't
connect for 5 seconds, then powercycle the box. This is useful because the
reboot is done via ssh, and if you can't ssh to the box because it is hung,
the reboot fails to reboot.

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