Stop exporting in devtest_testenv

We don't need to export variables in testenv, they are going to be
written into the JSON file, and we don't source testenv in devtest.sh,
so they fall out of scope when the script finishes executing anyway.

Change-Id: Ife9571d42ecb389cff445422169d8480512490e6
Merge "Stop exporting in devtest_testenv"