Remove race condition (in InstanceTypeProjects)

Soft delete all duplicate rows with the same (project_id, instance_type_id)
except one with the biggest value in `id` column.

Create UC on columns (project_id, instance_type_id, deleted)

Add tests for migration

Fix instance_type_access_add method
	Replace Select then Insert -> Try to Insert.

blueprint db-enforce-unique-keys

Change-Id: Id70509337e78f3bf778501f2c77aa03263580ef0
Merge "Remove race condition (in InstanceTypeProjects)"