Remove unused nova.db.api:network_get_by_bridge

Change-Id: Id75a46aec71cf08196f8444bae9957a001aa4fcc
Change CIDR column size on migration version 149

As discussed in review https://review.openstack.org/#/c/22238 cidr column needs
up to 43 characters in some cases, and this should be upgrade to avoid data get
lost.

Related to bug-1127696

Change-Id: I35d4565389d03fce86103289cf6447f824efeba0
Merge "Change CIDR column size on migration version 149"
Merge "Remove unused nova.db.api:network_get_by_bridge"