veyron/services/identity/identityd: Bind to localhost by default.
veyron/services/identity/identityd: Bind to localhost by default.

This change makes identityd bind to localhost:8125 by default to avoid
accidentally leaking identities. The --port flag is replaced with the more
commonly used --address flag at the same time.

Change-Id: I0cba6b83645eba18a90fa8e17febaa330a9b1aa5

vanadium/js,vanadium/js,vanadium/js,vanadium/js