Fix RM9305

* Fix does not allow a tenant to associate a network to a port
that does not belong to them unless it is publicnet or servicenet

* In existing UT, adds tenant_id to network models

* Added UT
Fixing IPv6 allocation with explicit IP

RM9413, RM9414, RM9419. Includes 2 new unit tests and some
cleaner boolean logic.
Merge pull request #228 from insequent/fix_port_ipv6

Fixing IPv6 allocation with explicit IP
Fix subnet quota checks

Allows admin changes unrestricted.

RM#9096
Merge pull request #229 from rackerlabs/subnet_quotas_fixed

Fix subnet quota checks
Merge pull request #230 from asadoughi/fixRM9305

Fix RM9305
Added config to show ipam_strategy

RM9561
Merge pull request #231 from rackerlabs/conf_show_ipam_strategy

Added config to show ipam_strategy
Use non-specific way to detect shared networks

RM9305
Merge pull request #232 from jmeridth/use_non_specific_shared_networks_detection

Use non-specific way to detect shared networks