String name() {
        return mode.name().toLowerCase();
    }
The mode the config proxy can be running with.

'default' mode is requesting config from server, serving from cache only when known config
and no new config having been sent from server. When in 'memorycache' mode, there is no connection
to a config source, the proxy serves from memory cache only.

@author hmusum
config-proxy/src/main/java/com/yahoo/vespa/config/proxy/Mode.java