Improve Hadoop-XrootD connector instrumentation and configuration for Spark
This PR introduces instrumentation for Spark and introfuces the environemnt variable XROOTDHADOOP_READAHEAD_SIZE that can be used to set the read ahead value.
This PR introduces instrumentation for Spark and introfuces the environemnt variable XROOTDHADOOP_READAHEAD_SIZE that can be used to set the read ahead value.