vp9_thread_test: fix 'had_error' assignment

worker hooks return false on error, fix the assignment in Execute() used
in the TestSerialInterface test

Change-Id: I93c2e45f270330ae6d35a3a303411c4ee0f31337
Initial AQ1 restructuring.

This is the first of a series of patches to restructure and
improve AQ mode 1 (variance based AQ).

Change-Id: Idcf693131a3ea2459dcfd957a54a65b971fa4a2a
Merge "vp9_thread_test: fix 'had_error' assignment"
Merge "Initial AQ1 restructuring."