qa/vstart_runner: keep cmd args as passed by user as well

qa/vstart_runner: keep cmd args as passed by user as well

We convert all cmd args to str and pass bash functions along to override
certain arguments in those command arguments. Let's save cmd args
without those bash functions since they can be useful later (for
example, printing cmd args in logs, which is the case in this patch.)

Signed-off-by: Rishabh Dave <ridave@redhat.com>