liblog: run in isolated mode, disable flaky tests

We disabled then re-enabled a set of tests believing that they were
stable; they were not, so we disable them again while we investigate
their stability.

A majority of tests filter the logs from logd based on pid, so running
in isolation helps them not see unexpected information from other test
runs.

Bug: 138876729
Bug: 142041379

Test: run via gtest with gtest_repeat=10 without failure
Test: run via atest 5x times without failure
Test: observe that isolated applies to both gtest and atest
Change-Id: I757d52dd3233323be9519625868b2fd2aaa41aeb