libmisc/btrfs: no sense trying to calculate 'btrfs' string

Signed-off-by: Serge Hallyn <shallyn@cisco.com>

libmisc/btrfs.c

@@ -32,7 +32,7 @@ static int run_btrfs_subvolume_cmd(const char *subcmd, const char *arg1, const c
 	int status = 0;
 	const char *cmd = btrfs_cmd();
 	const char *argv[] = {
-		strrchr(cmd, '/'),
+		"btrfs",
 		"subvolume",
 		subcmd,
 		arg1,
@@ -40,11 +40,6 @@ static int run_btrfs_subvolume_cmd(const char *subcmd, const char *arg1, const c
 		NULL
 	};
 
-	if (argv[0] == NULL)
-		argv[0] = cmd;
-	else
-		argv[0] = argv[0] + 1;
-
 	if (access(cmd, X_OK)) {
 		return 1;
 	}