In OVN 22.09, the option "localnet_learn_fdb" was added so that
localnet ports can learn MAC addresses and store them in the FDB
table. This avoids flooding issues for VMs on provider networks
when port security is disabled
Closes-Bug: #2012069
Change-Id: I93574b4fe9a79b649bfe755cf7e0697ccc7eb83a