hw/9pfs/virtio-9p-local.c: move v9fs_string_free() to below "err_out:"

When "goto err_out", 'v9fs_string' already was allocated, so still need
free 'v9fs_string' before return.

Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

hw/9pfs/virtio-9p-local.c

@@ -1059,9 +1059,9 @@ static int local_unlinkat(FsContext *ctx, V9fsPath *dir,
     }
     /* Remove the name finally */
     ret = remove(rpath(ctx, fullname.data, buffer));
-    v9fs_string_free(&fullname);
 
 err_out:
+    v9fs_string_free(&fullname);
     return ret;
 }