Separate and refactor RAM filter unit tests

The Aggregate RAM filter unit tests were accessing the database to
create Aggregate records. This patch moves all the RAM filter unit tests
out of test_host_filters.py into their own test file and updates the
unit tests to remove any database accesses entirely.

Change-Id: I93399e2af0d230fac9a7f1eb308adfa15e0a84f8
Merge "Separate and refactor RAM filter unit tests"