Modify Ethnologue tests to use registry redirection

On the build agents we set the environment variable
BUILDAGENT_SUBKEY. Unit tests should redirect the registry if they
see this variable. The Ethnologue unit tests didn't do this so far
which caused 6 tests to fail. Part of LT-13800.

Change-Id: Id723f9ef2f20752610e4ab2e495ca5152bab0c9a