Remove redundant tst_exit() calls.

Created with coccinelle patch:

@@ @@
tst_exit();
- tst_exit();

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
hotplug/cpu_hotplug: add it to run default

Fix test cases' exit status with TCONF on single cpu
machine, and add it to run default.

Signed-off-by: Xing Gu <gux.fnst@cn.fujitsu.com>