Rename screen logfiles

This renames the log files in logs/screen that contain timestamps to put
the timestamp after '.log' and '.log.summary' in the names.  This will
simplify devstack-gate's search for log files to copy to '*.log'.

dstat.txt is also renamed to dstat.log

Make LOGDIR and LOGFILE local

bp:devstack-logging-and-service-names
Change-Id: I02aba9ca82c117a1186dafc1d3c07aa04ecd1dde
diff --git a/stack.sh b/stack.sh
index 048e5d1..f42e68a 100755
--- a/stack.sh
+++ b/stack.sh
@@ -370,15 +370,14 @@
 fi
 
 if [[ -n "$LOGFILE" ]]; then
-    # First clean up old log files.  Use the user-specified ``LOGFILE``
-    # as the template to search for, appending '.*' to match the date
-    # we added on earlier runs.
-    LOGDIR=$(dirname "$LOGFILE")
-    LOGFILENAME=$(basename "$LOGFILE")
-    mkdir -p $LOGDIR
-    find $LOGDIR -maxdepth 1 -name $LOGFILENAME.\* -mtime +$LOGDAYS -exec rm {} \;
+    # Clean up old log files.  Append '.*' to the user-specified
+    # ``LOGFILE`` to match the date in the search template.
+    local logfile_dir="${LOGFILE%/*}"           # dirname
+    local logfile_name="${LOGFILE##*/}"         # basename
+    mkdir -p $logfile_dir
+    find $logfile_dir -maxdepth 1 -name $logfile_name.\* -mtime +$LOGDAYS -exec rm {} \;
     LOGFILE=$LOGFILE.${CURRENT_LOG_TIME}
-    SUMFILE=$LOGFILE.${CURRENT_LOG_TIME}.summary
+    SUMFILE=$LOGFILE.summary.${CURRENT_LOG_TIME}
 
     # Redirect output according to config
 
@@ -399,8 +398,8 @@
 
     echo_summary "stack.sh log $LOGFILE"
     # Specified logfile name always links to the most recent log
-    ln -sf $LOGFILE $LOGDIR/$LOGFILENAME
-    ln -sf $SUMFILE $LOGDIR/$LOGFILENAME.summary
+    ln -sf $LOGFILE $logfile_dir/$logfile_name
+    ln -sf $SUMFILE $logfile_dir/$logfile_name.summary
 else
     # Set up output redirection without log files
     # Set fd 3 to a copy of stdout. So we can set fd 1 without losing