syscalls/waitpid02: check if fork failed

Break the test if fork failed. Or this test case will kill a lot of
processes on the system (when -1 ends up passed as a pid to kill()).

Signed-off-by: Han Pingtian <hanpt@linux.vnet.ibm.com>
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>
1 file changed