Moved denoiser frame copy/updates out of loopfilter thread

The loopfilter thread from the previous frame can be running while
starting the current frame.  cpi->Source will change during this time causing
the wrong data to be copied.  The refresh_x_frame flags also change, which
will cause incorrect updates of the denoised buffers.

Change-Id: I7d982b4fcb40a0610801332aa85f3b792c64e4c3