selftests/clone3: Correct log message for waitpid() failures

When logging an error from calling waitpid() on the child we print a
misleading error message saying that the error we report was returned by
the chilld. Fix this to say the error is from waitpid().

Applied after fixing merge conflict:
Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

tools/testing/selftests/clone3/clone3.c

@@ -95,7 +95,7 @@ static int call_clone3(uint64_t flags, size_t size, enum test_mode test_mode)
 			getpid(), pid);
 
 	if (waitpid(-1, &status, __WALL) < 0) {
-		ksft_print_msg("Child returned %s\n", strerror(errno));
+		ksft_print_msg("waitpid() returned %s\n", strerror(errno));
 		return -errno;
 	}
 	if (!WIFEXITED(status)) {