MT#3997 Add via_route column to voip_peer_hosts

This defines a route set to be executed on the way out to a peer after
the lb.

db_scripts/diff/15023.down

@@ -0,0 +1,3 @@
+USE provisioning;
+
+ALTER TABLE voip_peer_hosts DROP COLUMN via_route;

db_scripts/diff/15023.up

@@ -0,0 +1,4 @@
+USE provisioning;
+
+ALTER TABLE voip_peer_hosts 
+  ADD COLUMN via_route VARCHAR(255) DEFAULT NULL AFTER weight;