vp9: Adjust some early exits in nonrd-pickmode.
vp9: Adjust some early exits in nonrd-pickmode.

Condition some early exitis in nonrd-pickmode on the
motion vector, to make sure we always test (0, 0) for
inter-layer prediction.

Change-Id: Id0e790ecc75ccfb7031d3e8786ccdd13781d81fe

webmproject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,ShiftMediaProject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx