Fallback to Quota Conf Driver if Quotas table is not defined

commit de15e0b9c5 enabled Quota DB driver default considering
production environments, but it breaks plugins without per-tenant
quota extension. In these plugin quotas tables is not loaded.

This commit fallbacks to ConfDriver if Quota model is not loaded by
checking neutron.db.quota_db which defines Quota model is imported.

Change-Id: Idaaaa9810598cfd3e5ce70020f498643b4819d16
Closes-Bug: #1236993
Fix auto-deletion of ports when deleting subnets in ML2

When a subnet is deleted, certain ports referencing it are
auto-deleted. The implementation of NeutronDBPluginV2.delete_subnet()
does this at the DB level, so ML2's mechanism drivers were not being
called.

Ml2Plugin.delete_subnet() is changed to not use the base class's
method, and to auto-delete ports by calling its own delete_port()
method outside of the transaction. A loop avoids race conditions with
ports being asynchronously added to the subnet.

The logic in Ml2Plugin.delete_network() is also fixed to properly
handle auto-deleting ports and subnets, and debug logging is added to
the various delete methods.

Closes-Bug: 1234195
Partial-Bug: 1235486
Change-Id: I6d74f89d39ea8afe6915f1d2f9afdf66c0076f5a
Imported Translations from Transifex

Change-Id: Iadb02e0009605ba739d6c7e6ccbe1e62331f94fe
Fix migration

In migration 338d7508968c_vpnaas_peer_address_ was mistake in
usage alter_column's parameter type_.

Closes-Bug: #1238561

Change-Id: I6e0eb8260cf5e8d8f557b174c7985e2f7ca1c912
Use L3 api from vpn ipsec driver via service plugin

VPNaaS and ML2 plugin won't work, because ML2 plugin
supports service version of L3.
In this commit, we modify ipsec driver to use L3 plugin.
This is also backward compatible change, because if L2 plugin
supports L3 get_service_plugin API returns L2 plugin.

Fixes bug 1238846

Change-Id: I36e541bb2e3e1df2e01f73a74f3e9005af6c38b7
Note: Exsiting unit test covers this change
Merge "Fix migration"
Merge "Fix auto-deletion of ports when deleting subnets in ML2"
Merge "Fallback to Quota Conf Driver if Quotas table is not defined"
DB migration upgrade/downgrade not employed for brocade-plugin

Fixes bug: 1238921

Change-Id: I441d82a92588d7318a2f3b725643bc1b050a2c9c
Merge "DB migration upgrade/downgrade not employed for brocade-plugin"
Merge "Use L3 api from vpn ipsec driver via service plugin"
Imported Translations from Transifex

Change-Id: I7f3cd275f90661f52310abf0f353ed87a81f6db1