Pull dstat logic into its own function so grenade can use it

In order to use dstat on the new side of grenade, pull dstat code into
its own lib with the function start_dstat

Change-Id: I5c908d594a6f3a90ed4b3f744002bf606841cf07

lib/dstat

@@ -0,0 +1,41 @@
+# lib/apache
+# Functions to start and stop dstat
+
+# Dependencies:
+#
+# - ``functions`` file
+
+# ``stack.sh`` calls the entry points in this order:
+#
+# - start_dstat
+# - stop_dstat
+
+# Save trace setting
+XTRACE=$(set +o | grep xtrace)
+set +o xtrace
+
+
+# Defaults
+# --------
+# for DSTAT logging
+DSTAT_FILE=${DSTAT_FILE:-"dstat.txt"}
+
+
+# start_dstat() - Start running processes, including screen
+function start_dstat {
+    # A better kind of sysstat, with the top process per time slice
+    DSTAT_OPTS="-tcmndrylp --top-cpu-adv"
+    if [[ -n ${SCREEN_LOGDIR} ]]; then
+        screen_it dstat "cd $TOP_DIR; dstat $DSTAT_OPTS | tee $SCREEN_LOGDIR/$DSTAT_FILE"
+    else
+        screen_it dstat "dstat $DSTAT_OPTS"
+    fi
+}
+
+# stop_dstat() stop dstat process
+function stop_dstat {
+    screen_stop dstat
+}
+
+# Restore xtrace
+$XTRACE

stack.sh

@@ -323,9 +323,6 @@ SYSLOG=`trueorfalse False $SYSLOG`
 SYSLOG_HOST=${SYSLOG_HOST:-$HOST_IP}
 SYSLOG_PORT=${SYSLOG_PORT:-516}
 
-# for DSTAT logging
-DSTAT_FILE=${DSTAT_FILE:-"dstat.txt"}
-
 # Use color for logging output (only available if syslog is not used)
 LOG_COLOR=`trueorfalse True $LOG_COLOR`
 
@@ -369,6 +366,7 @@ source $TOP_DIR/lib/heat
 source $TOP_DIR/lib/neutron
 source $TOP_DIR/lib/baremetal
 source $TOP_DIR/lib/ldap
+source $TOP_DIR/lib/dstat
 
 # Extras Source
 # --------------
@@ -948,12 +946,7 @@ init_service_check
 # -------
 
 # A better kind of sysstat, with the top process per time slice
-DSTAT_OPTS="-tcmndrylp --top-cpu-adv"
+start_dstat
-if [[ -n ${SCREEN_LOGDIR} ]]; then
-    screen_it dstat "cd $TOP_DIR; dstat $DSTAT_OPTS | tee $SCREEN_LOGDIR/$DSTAT_FILE"
-else
-    screen_it dstat "dstat $DSTAT_OPTS"
-fi
 
 # Start Services
 # ==============

unstack.sh

@@ -162,6 +162,8 @@ if is_service_enabled trove; then
     cleanup_trove
 fi
 
+stop_dstat
+
 # Clean up the remainder of the screen processes
 SCREEN=$(which screen)
 if [[ -n "$SCREEN" ]]; then