Unable to create subnets with the same CIDR in different tenants

Issue

• A user is unable to create a subnet with the CIDR of 192.168.1.0/24 when a user in another tenant has already created a seperate subnet with the same CIDR.
• The following error is reported in the nuetron server.log:

INFO neutron.db.db_base_plugin_v2 [req-5f4d3802-9368-4e4c-8652-cc6bac4b9a5c None] Validation for CIDR: 192.168.1.0/24 failed - overlaps with subnet 387912c4-10e8-4951-85e0-47c00cde6333 (CIDR: 192.168.1.0/24)                                                                                                                                                 
INFO neutron.api.v2.resource [req-5f4d3802-9368-4e4c-8652-cc6bac4b9a5c None] create failed (client error): Invalid input for operation: Requested subnet with cidr: 192.168.1.0/24 for network: 3c53d7fe-6978-4ead-92af-55c56db0336b overlaps with another subnet.