If renderer_blocked is set do not call virtio_gpu_virgl_reset().
Instead set a flag indicating that virglrenderer needs a reset.
When renderer_blocked gets cleared do the actual reset call.

Without this we can trigger an assert in spice due to calling
spice_qxl_gl_scanout() while another operation is still running:

spice_qxl_gl_scanout: condition `qxl_state->gl_draw_cookie == GL_DRAW_COOKIE_INVALID' failed
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>
Message-id: 20190314115358.26678-2-kraxel@redhat.com