simply workload exec code

Now workload process calling pause() to wait ktapvm send signal.

we need to recheck this design in future, possibly this design
is not quite safely.

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>
Rewrite ktap option parse code

kill old option parsing code doesn't fit ktap specific
option handling, for example workload cmd option, so use
a hand-write option parser instead.

Now invoke workload should be like:

ktap scripts/syscalls.kp -- ls -a

Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@gmail.com>