Add NetworkStackModuleTest annotation on the specific test case.

EthernetTetheringTest#testTetherZeroLengthDhcpPacket requires the latest
NetworkStack module, otherwise, the test will fail due to the loss of
the fix. Apply @NetworkStackModuleTest to exclude this testcase from
target test suite CtsTetheringTestLatestSdk.

Bug: 283200648
Test: atest CtsTetheringTestLatestSdk
Change-Id: Iebfb043e2b71427a6feaf90788fe79b6ab6b678d