encode_api_test: quiet static analysis warning
encode_api_test: quiet static analysis warning

in ConfigChangeThreadCount(); initialize cfg as the static analyzer can
assume AlwaysTrue() within EXPECT_NO_FATAL_FAILURE may return false
causing InitCodec() not to be called.

test/encode_api_test.cc|321 col 3| warning: 1st function call argument
is an uninitialized value [core.CallAndMessage]
  video.SetSize(cfg.g_w, cfg.g_h);

Bug: b/229626362
Change-Id: I54899ed0a207ca685416bed3a0e9c9644668e163

webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx,webmproject/libvpx