sf: vds: Queue Sink buffer during invalidate

commit id:f3c07d4f didnt queue sink
buffer if there is no screen update on virtual displays.

This was required to support nested virtual displays. However,
this breaks Miracast WFD Sink initiated pause/resume functionality.

Allow Queueing sink buffers if mForceHwcCopy is true.

Change-Id: Id29c7ccedc0c10956b5af3a2d3e8b72966a4dfc0