Protected trace logging statement in DefaultConnectionPool with check for whether trace logging is enabled.

Author: jyemin

driver-core/src/main/com/mongodb/connection/DefaultConnectionPool.java

@@ -246,7 +246,9 @@ private PooledConnection getPooledConnection(final long timeout, final TimeUnit
             internalConnection = pool.get(timeout, timeUnit);
         }
         connectionPoolListener.connectionCheckedOut(new ConnectionEvent(internalConnection.getDescription().getConnectionId()));
-        LOGGER.trace(format("Checked out connection [%s] to server %s", getId(internalConnection), serverId.getAddress()));
+        if (LOGGER.isTraceEnabled()) {
+            LOGGER.trace(format("Checked out connection [%s] to server %s", getId(internalConnection), serverId.getAddress()));
+        }
         return new PooledConnection(internalConnection);
     }