Sync db.models.Security* and db.models.Volume*.

This patch syncs models with migrations.

Change-Id: I2e4a4cf28376d933be47bc496933e6964e19a56e
Sync 10 DB models and migrations.

This patch syncs models with migrations for:
- BlockDeviceMapping
- IscsiTarget
- FixedIp
- FloatingIp
- KeyPair
- Migration
- Network
- ProviderFirewallRule
- Reservation
- S3Image

Blueprint: db-sync-models-with-migrations

Change-Id: I8e16375fe48744513167272e956cdbfdbfd8af23
Merge "Sync 10 DB models and migrations."
Merge "Sync db.models.Security* and db.models.Volume*."