tst_cmd: Fix exit in search for program in $PATH

The check is executed before fork() so we have to do return instead of
exit() otherwise we exit the library process.

Fixes: 105d283 ("lib/tst_cmd_*(): Search for program in $PATH")

Signed-off-by: Cyril Hrubis <[email protected]>

Author: metan-ucw

lib/tst_cmd.c

@@ -64,7 +64,7 @@ int tst_cmd_fds_(void (cleanup_fn)(void),
 			tst_brkm(TCONF, cleanup_fn, "Couldn't find '%s' in $PATH at %s:%d", argv[0],
 				 __FILE__, __LINE__);
 		else
-			_exit(255);
+			return 255;
 	}
 
 	pid_t pid = vfork();