Use test tag of the subprocess if the one in parent process is not set yet

Versioned TF runs the actual test in a subprocess. The parent process doesn't
have the test tag of the actual test. This change allows the subprocess to
report the test tag through SubprocessResultsReporter. The parent process then
can set the test tag in SubprocessTestResultsParser, unless its test tag is set
already.

Bug: 36364024
Test: unittest, local run test
(need local change in setBuild to copy over local TF code.)
tradefed.sh run  google/template/lab-base-versioned --tf-command-line \
      "--template:map test=tf/fake --run \"test.class=P\" \
       --test-tag TagInSubProcess \
       --branch git_master --build-flavor angler-userdebug \
       --build-os linux --build-id 3764429  --log-level-display VERBOSE " \
      --branch git_master \
      --build-flavor test_suites_x86_64 --build-os fastbuild3d_linux \
      --build-id 3764429 --log-level-display VERBOSE

Change-Id: I4f19f1b7cc6fd2fc53176e71f570fd58c523da31
4 files changed