tree-wide: Update to new libglnx fd APIs

This ends up a lot better IMO.  This commit is *mostly* just
`s/glnx_close_fd/glnx_autofd`, but there's also a number of hunks like:

```
-  if (self->sysroot_fd != -1)
-    {
-      (void) close (self->sysroot_fd);
-      self->sysroot_fd = -1;
-    }
+  glnx_close_fd (&self->sysroot_fd);
```

Update submodule: libglnx

Closes: #1259
Approved by: jlebon

src/libostree/ostree-sysroot-cleanup.c

@@ -282,7 +282,7 @@ cleanup_old_deployments (OstreeSysroot       *self,
       if (!g_hash_table_lookup (active_deployment_dirs, deployment_path))
         {
           struct stat stbuf;
-          glnx_fd_close int deployment_fd = -1;
+          glnx_autofd int deployment_fd = -1;
 
           if (!glnx_opendirat (self->sysroot_fd, deployment_path, TRUE,
                                &deployment_fd, error))