Updates to how shards are discovered while the module is running

SHOW DATABASES now takes notice of the state of the backends
Added scripts for sharding test preparation and local port blocking

server/modules/routing/dbshard/test/portblock.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+if [ $# -lt 1 ]
+then
+    echo "Usage $0 <port to block>"
+    exit 1
+fi
+sudo iptables -I INPUT 1 -i lo -p tcp --dport $1 -j DROP
+sudo iptables -I INPUT 1 -i lo -p tcp --sport $1 -j DROP
+echo "Traffic to port $1 blocked."