Fix ContainerBroker to initialize as policy-0 on policy_stat
table in default when storage_policy_index argument is NOT given.
Current ContainerBroker makes policy-1 stats in default because
the "None" value will be passed through to the last function of
db access query (i.e. a query like as "INSERT INTO policy_stat
(storage_policy_index) VALUES (None)" will appear) which results
in a row "(1, 0, 0)" (the first value is the policy index) by
the PRIMARY KEY constraint on sqlite.
In worst case, container db keeps two policies, and then, ContainerBroker.get_info
might return invalid (non-touched) policy_stat information as container information.
(See tests in detail)
When using ContainerBroker with no storage_policy_index argument,
it should always act policy-0 simply.
Note that this patch doesn't affect immediately Swift behavior because
current swift ensures to use policy-0 on "Container-Server" when invalid
policy (includes None) is given. However, we should recheck also in
ContainerBroker for safety to prevent the unfortunate behavior above.
Change-Id: If64f0c94c069a2cc3140c99f21b8d371c183e28a
16b435a4a8