Exclude testGetNeighborsQuery from NetworkStackCoverageTests.

sepolicy gates RTM_GETNEIGH{TBL} with a new permission nlmsg_getneigh
and block access from untrusted_apps, but NetworkStackCoverageTests
uses the same UID with NetworkStack module, so it still has the
permission to send RTM_GETNEIGH(context: u:r:network_stack:s0<00>),
which causes the test always fails. Add the same assumeFalse check
for tests with network_stack context.

Bug: 283346574
Test: atest NetworkStackCoverageTests
Change-Id: Iaf652841bb9868783c924aa22fdf0c4f07e1e391