There is a problem with the ImageReader formats used by the
SSIM helper that only occurs for Nexus 5 API 21, so as a workaround
we can skip the SSIM calculation on Nexus 5 API 21.
This skips just the SSIM calculation (by setting the value to
1.0 instead and logging). The tests still run when SSIM is skipped
so that we can detect other failures.
PiperOrigin-RevId: 450903183
