packaging: dbscripts: rename add_vm_migration_downtime.sql

from 03_04_0480_add_vm_migration_downtime.sql
to 03_04_0490_add_vm_migration_downtime.sql
to solve a conflict.

Change-Id: Ia7bc6269f620d6dbf874b9700c92d0a2222569e7
Signed-off-by: Yedidyah Bar David <didi@redhat.com>