Correctly log elapsed milliseconds in CentralDogmaBeanFactory (line…

…#991)

Motivation:

When the elapsed time in `CentralDogmaBeanFactory#get()` is logged, it prints nanoseconds with `ms` unit.

Modifications:

- Convert the elapsed time to milliseconds before logging.

Result:

The logs correctly display the elapsed time of obtaining the initial value.

client/java/src/main/java/com/linecorp/centraldogma/client/updater/CentralDogmaBeanFactory.java

@@ -328,7 +328,7 @@ public <T> T get(T defaultValue, Class<T> beanType, Consumer<T> changeListener,
                     throw ex;
                 }
             }
-            final long elapsedMillis = System.nanoTime() - t0;
+            final long elapsedMillis = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - t0);
             logger.debug("Initial value of {} obtained in {} ms: rev={}",
                          settings, elapsedMillis, latest.revision());
         }