Add test for LocalCallingIdentity changes

With the introduction of LocalCallingIdentity caching across requests,
in I9811efca7af223eaf99e28c79a948eca41579dbe it becomes very important
to ensure that any permission changes on a uid trigger cache
invalidation.

Minor refactoring of TestUtils to re-use utils

Test: atest FuseDaemonHostTest
Bug: 148904081
Change-Id: I16d6c74f2164745b9f817dd5dac3cbbb2ea9664b
7 files changed