ktest: Set buildonly=1 for CONFIG_BISECT_TYPE=build

Rather than adding a third copy of the same logic, rework it to cover
all three buildonly cases at once.

In the future, please consider using the same variable to perform the
same function regardless of context...

Link: http://lkml.kernel.org/r/20170717001630.10518-2-swood@redhat.com



Signed-off-by: Scott Wood <swood@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>