In LocalBookkeeper, Zookeeper server and client use different host addresses

In LocalBookkeeper, the Zookeeper server is started at 127.0.0.1 and the client tries to derive the localhost address using getLocalHost API. This has a few issues:
1. There is a possibility of using the ipv6 address for localhost and hence the client will try connecting to ::1, 2181 rather than 127.0.0.1:2181 (this happens commonly on OSX)
2. The getLocalHost API could sometimes return non-loopback addresses as well.

Since the 'localbookie' mode is used with the zookeeper in the same machine, we should use loopback addresses for all invocations. The patch does just that.