Fix CDEF strength search
Fix CDEF strength search

Previous code was using options selected for N=8 rather than the chosen
number of options.

low-latency, cpu=4:

  PSNR | PSNR Cb | PSNR Cr | PSNR HVS |    SSIM | MS SSIM | CIEDE 2000
0.0077 |  0.0286 | -0.1166 |  -0.0059 | -0.0479 |  0.0025 |    -0.0101

Properly save the best strengths

Change-Id: I629e929c2bc7a0a9592a9e49bfd7898d95174235

smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,smarter/aom,smarter/aom,smarter/aom,smarter/aom,GrokImageCompression/aom,smarter/aom,GrokImageCompression/aom,GrokImageCompression/aom,GrokImageCompression/aom