Remove functional migration script about external tables
Remove functional migration script about external tables

This test has run out of its useful purpose. It was meant to protect
accidental schema changes involving external tables. After a few cycles
now, it is very unlikely that human error will not be spotted during
code review, where external tables are referenced/modified during Neutron
core schema migrations.

Putting effort into fixing the BGP removal corner case is not worth it,
and it is probably best to get rid of the test entirely.

Change-Id: I71da8ea5aa5513056a0dc62b6ac9d8c0394583dd
Related-bug: 1466704

cloudbase/neutron,mahak/neutron,sebrandon1/neutron,openstack/neutron,bigswitch/neutron,noironetworks/neutron,sebrandon1/neutron,mahak/neutron,cloudbase/neutron,igor-toga/local-snat,mahak/neutron,noironetworks/neutron,openstack/neutron,eayunstack/neutron,eayunstack/neutron,bigswitch/neutron,huntxu/neutron,igor-toga/local-snat,huntxu/neutron,openstack/neutron