Test upscaling as well as downscaling

Fixes a bug in vp9_set_internal_size() that prevented returning to
the unscaled state. Updated the ResizeInternalTest to scale both
down and up. Added a check that all frames are within 2.5% of the
quality of the initial keyframe.

Change-Id: I3b7ef17cdac144ed05b9148dce6badfa75cff5c8