Sometimes hostname resolution will fail.  Don't break ioloop if it does

After a network failure, term() can hang.  The problem seems to be with address.resolve() failing in add_reconnect_timer().  This can, and does, throw an IllegalArgumentException if address resolution fails which then breaks the ioloop.  I've made a small patch that catches this exception and ignores it.  The patch also ensures that open() throws an IOException if the resolved address is null.