Consider subnets across all networks within project when checking quota limit for subnets

Change-Id: I441f824ddadbfbbe8d9511509deb28ac57e24c12
Closes-Bug: 1355341
(cherry picked from commit 08691b1c096e076a19fa5b3d74363e611673830f)
Merge "Consider subnets across all networks within project when checking quota limit for subnets"