HDFS-7222. Expose DataNode network errors as a metric. (Charles Lamb via wang)

(cherry picked from commit 86cad007d7d6366b293bb9a073814889081c8662)
HDFS-7227. Fix findbugs warning about NP_DEREFERENCE_OF_READLINE_VALUE in SpanReceiverHost (cmccabe)
(cherry picked from commit 7ab754545dca16518e8fe9353ef69b77f365426b)
HDFS-7232. Populate hostname in httpfs audit log (Zoran Dimitrijevic via aw)