void setPoolName(String poolName) {
      this.poolName = poolName;
    }
When we kill a query without killing a session, we need two things to come back before reuse.
First of all, kill query itself should come back, and second the user should handle it
and let go of the session (or, the query could finish and it could give the session back
even before we try to kill the query). We also need to handle cases where the user doesn't
like the session even before we kill it, or the kill fails and the user is happily computing
away. This class is to collect and make sense of the state around all this.
ql/src/java/org/apache/hadoop/hive/ql/exec/tez/WorkloadManager.java