vtest: fix fencing

Let's be a little less conservative then QEMU -- fence only
on draw calls and possible fence creations.

Can we do even better, and fence only when Gallium requests
VIRGL_BIND_CUSTOM?  Someone should look into this, but let's
get this landed to unblock the CQ.

Reviewed-by: Gert Wollny <gert.wollny@collabora.com>
Signed-off-by: Jakob Bornecrantz <jakob@collabora.com>

vtest/vtest_renderer.c

@@ -736,7 +736,6 @@ int vtest_resource_busy_wait(UNUSED uint32_t length_dw)
    uint32_t reply_buf[1];
    bool busy = false;
 
-   vtest_renderer_create_fence();
    ret = vtest_block_read(renderer.in_fd, &bw_buf, sizeof(bw_buf));
    if (ret != sizeof(bw_buf)) {
       return -1;

vtest/vtest_server.c

@@ -302,6 +302,12 @@ static void vtest_main_run_renderer(int in_fd, int out_fd)
          err = 7;
          break;
       }
+
+      /* GL draws are fenced, while possible fence creations are too */
+      if (header[1] == VCMD_SUBMIT_CMD || header[1] == VCMD_RESOURCE_CREATE ||
+          header[1] == VCMD_RESOURCE_CREATE2)
+         vtest_renderer_create_fence();
+
    } while (1);
 
    fprintf(stderr, "socket failed (%d) - closing renderer\n", err);