fixed database downgrade bug from v0.7 to v0.6

Signed-off-by: tierno <alfonso.tiernosepulveda@telefonica.com>
diff --git a/database_utils/migrate_mano_db.sh b/database_utils/migrate_mano_db.sh
index 3364d4f..86a3b77 100755
--- a/database_utils/migrate_mano_db.sh
+++ b/database_utils/migrate_mano_db.sh
@@ -445,7 +445,6 @@
     for table in datacenters datacenter_nets instance_nets instance_scenarios instance_vms instance_vnfs interfaces nets nfvo_tenants scenarios sce_interfaces sce_nets sce_vnfs tenants_datacenters vim_tenants vms vnfs uuids
     do
          echo -en "        $table               \r"
-         echo "ALTER TABLE $table ADD COLUMN created_at_ DOUBLE NOT NULL after created_at;" | $DBCMD || ! echo "ERROR. Aborted!" || exit -1
          echo "ALTER TABLE $table ADD COLUMN created_at_ TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP after created_at;" | $DBCMD || ! echo "ERROR. Aborted!" || exit -1
          echo "UPDATE $table SET created_at_=from_unixtime(created_at);" | $DBCMD || ! echo "ERROR. Aborted!" || exit -1
          echo "ALTER TABLE $table DROP COLUMN created_at, CHANGE COLUMN created_at_ created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP;" | $DBCMD || ! echo "ERROR. Aborted!" || exit -1