allow better diagnostic of DNS problem by timing CouchbaseNode hostname

Since it has been suspected that reverse DNS lookup can be the culprit in some connection delays, upon calling CouchbaseNode.connect for the first time, this case could be sanity-checked and logged to aid diagnostics:

the InetAddress.getHostName() will attempt to resolve and cache the hostname if it wasn't filled at construction, using a reverse DNS lookup.

the connect method starts by a log line, which calls getHostName()

prior to that step, the method should be called explicitely enclosed within a timing measurement, and a WARN log be issued stating that DNS resolution took N milliseconds (if above a reasonable threshold).