Convert tetheroffload hal test to use VtsHalHidlTargetTestEnvBase

* This allow VTS to test tetheroffload hal against all service
  implmentations registered with different service name.

Bug: 64203181
Test: make vts
      vts-tradefed run vts -m VtsHalTetherOffloadConfigV1_0Target
      vts-tradefed run vts -m VtsHalTetherOffloadControlV1_0Target

Change-Id: I0b4f3cf4abd3ffbd15cef7c2126ce6252a65a28e