Validate local_ip for OVS agent is actual ip address

tunnel_sync() writes this value into ovsdb and value is not validated. In
case non-ip value is written into ovsdb row must be deleted manually.

Change-Id: I57eee81e6821eb2cb26b3d07a39bc94b81243570
Closes-bug: #1284684
Drop and recreate FK if adding new PK to routerl3bindings

Since MySQL 5.6 FK columns cannot be altered. As a workaround we can
drop the FK before ALTER COLUMN and then recreate it.

Change-Id: Icd1b3075cf29a6b0c477a4ddea2e6ebee91baef8
Closes-Bug: 1384555
enable H237 check

Remove the remove use of 'new' module by properly patching the instance
object.  Additionally, enable the H237 (module is removed in Python 3) check

Change-Id: I7407600478de218a4294c4bfd774cd4cf7e1741e
Partial-Bug: 1329017
Merge "enable H237 check"
Merge "Drop and recreate FK if adding new PK to routerl3bindings"
Merge "Validate local_ip for OVS agent is actual ip address"