run dstat with run_process

It is not clear to me why this can't use run_process?  Currently we
end up with two log-files both with the same thing

- dstat.txt.gz which comes from the "tee" and is symlinked into
  SCREEN_LOGDIR, so gets picked-up by the gate scripts
- screen-dstat.txt.gz which comes from screen_it

Change-Id: I00b9e09b8d44f72ff14e69dc6e4a4bd5e2a0439e

lib/dstat

@@ -16,34 +16,16 @@
 XTRACE=$(set +o | grep xtrace)
 set +o xtrace
 
-
-# Defaults
-# --------
-# for DSTAT logging
-DSTAT_FILE=${DSTAT_FILE:-"dstat.log"}
-
-
 # start_dstat() - Start running processes, including screen
 function start_dstat {
     # A better kind of sysstat, with the top process per time slice
     DSTAT_OPTS="-tcmndrylpg --top-cpu-adv --top-io-adv"
-    if [[ -n ${LOGDIR} ]]; then
-        screen_it dstat "cd $TOP_DIR; dstat $DSTAT_OPTS | tee $LOGDIR/$DSTAT_FILE"
-        if [[ -n ${SCREEN_LOGDIR} && ${SCREEN_LOGDIR} != ${LOGDIR} ]]; then
-            # Drop the backward-compat symlink
-            ln -sf $LOGDIR/$DSTAT_FILE ${SCREEN_LOGDIR}/$DSTAT_FILE
-        fi
-    else
-        screen_it dstat "dstat $DSTAT_OPTS"
-    fi
+    run_process dstat "dstat $DSTAT_OPTS"
 }
 
 # stop_dstat() stop dstat process
 function stop_dstat {
-    # dstat runs as a console, not as a service, and isn't trackable
-    # via the normal mechanisms for DevStack. So lets just do a
-    # killall and move on.
-    killall dstat || /bin/true
+    stop_process dstat
 }
 
 # Restore xtrace