persistent_create_policy_with_rules method added to agnostic runtime
to transactionally create policy along with rules. The main work is
done by the persistent_insert_rules method extended to allow creation
of the target policy along with the rule inserts.
Database transactions added in persistent_insert_rules to make sure
all changes (policy add and rules insert) can be committed or rolled
back together.
DB table locking expanded to the `policies` table in the policy
creation case to prevent conflicting policy changes from other nodes.
policy_model add_item API method extended to accept policy item with
rules, (exclusive) or parameter specifying ID of library policy to
activate.
Partially implements: blueprint policy-library
Partial-Bug: 1693622
Change-Id: I2a83ac11b7014d417ff7553f602a8bb96a9adc34
94fdc38c86