xfstests: fix src/seek_sanity_test -t option

_require_seek_data_hole() does not work because
the -t (test) option of seek_sanity_test is broken,
because of an early check for (argc != 2):

# src/seek_sanity_test -t foo
Usage: src/seek_sanity_test base_file_path

So _require_seek_data_hole() doesn't see the
"Kernel does not support" string it's looking for,
and passes the check.

So rather than _notrun-ing the test, it proceeds to
fail with noisy errors.

Fix that, make a common usage() function, and check for
too many args as well.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Jie Liu <jeff.liu@oracle.com>
Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Rich Johnston <rjohnston@sgi.com>

src/seek_sanity_test.c

@@ -656,6 +656,12 @@ out:
 	return ret;
 }
 
+void usage(char *cmd)
+{
+	fprintf(stdout, "Usage: %s [-t] base_file_path\n", cmd);
+	exit(1);
+}
+
 int main(int argc, char **argv)
 {
 	int ret = -1;
@@ -664,23 +670,20 @@ int main(int argc, char **argv)
 	int check_support = 0;
 	int numtests = sizeof(seek_tests) / sizeof(struct testrec);
 
-	if (argc != 2) {
-		fprintf(stdout, "Usage: %s base_file_path\n", argv[0]);
-		return ret;
-	}
-
 	while ((opt = getopt(argc, argv, "t")) != -1) {
 		switch (opt) {
 		case 't':
 			check_support++;
 			break;
 		default:
-			fprintf(stderr, "Usage: %s [-t] base_file_path\n",
-				argv[0]);
-			return ret;
+			usage(argv[0]);
 		}
 	}
 
+	/* should be exactly one arg left, the filename */
+	if (optind != argc - 1)
+		usage(argv[0]);
+
 	base_file_path = (char *)strdup(argv[optind]);
 
 	ret = test_basic_support();