Support beta 4 system images.

Beta 4 system images only understand the NETWORK_TEST_RESULT_*
constants and not the new NETWORK_VALIDATION_RESULT_* constants.
When talking to such a build, use the older constants.

Bug: 134923144
Test: atest NetorkStackTests
Test: beta 4 OS build validates
(patched from Icf28c5dcd622c89c411a87b63d2ce4aa7488d082 using:
git -C ~/other-branch-repo/frameworks/base/ show -p | patch -p3)
Change-Id: I749a228711b1b7ea9b5f87be5da3b026aaed0807