Switch leftover logs to slf4j format in BlockManager.java

HDFS-7706 Switch BlockManager logging to use slf4j. But the logging formats were not modified appropriately. For example:
if (LOG.isDebugEnabled())

{ LOG.debug("blocks = " + java.util.Arrays.asList(blocks)); }

These codes should be modified to:
LOG.debug("blocks = {}", java.util.Arrays.asList(blocks));