Due to change in command line to sample encoder from:
7eff8f3 Update to vpx_temporal_svc_encoder command line.
This caused the tests in vpx_temporal_svc_encoder.sh to fail.
Change-Id: Ic667da81955ad117d04610af21877fed1d4f188f
Specifying the --prefix command line arg executes all test programs within the
context of the prefix string, which is assigned to VPX_TEST_PREFIX.
All test functions updated to include VPX_TEST_PREFIX in their eval command.
Change-Id: I2e215cc8f216048edf3269db02a6b5660fe32318