Deprecate SCREEN_LOGDIR in favor of LOGDIR

This is the first step in the log file cleanup.  If SCREEN_LOGDIR
is still set, symlinks will be created in the old screen log directory
so things like the devstack-gate log collector continues to work.

bp:logging-and-service-names
Change-Id: I3ac796e322a18dbd0b8b2310a08310ca159d7613
diff --git a/stack.sh b/stack.sh
index aeaaf60..558b07e 100755
--- a/stack.sh
+++ b/stack.sh
@@ -373,10 +373,8 @@
 # Append '.xxxxxxxx' to the given name to maintain history
 # where 'xxxxxxxx' is a representation of the date the file was created
 TIMESTAMP_FORMAT=${TIMESTAMP_FORMAT:-"%F-%H%M%S"}
-if [[ -n "$LOGFILE" || -n "$SCREEN_LOGDIR" ]]; then
-    LOGDAYS=${LOGDAYS:-7}
-    CURRENT_LOG_TIME=$(date "+$TIMESTAMP_FORMAT")
-fi
+LOGDAYS=${LOGDAYS:-7}
+CURRENT_LOG_TIME=$(date "+$TIMESTAMP_FORMAT")
 
 if [[ -n "$LOGFILE" ]]; then
     # Clean up old log files.  Append '.*' to the user-specified
@@ -428,6 +426,7 @@
 # ``screen-$SERVICE_NAME-$TIMESTAMP.log`` in that dir and have a link
 # ``screen-$SERVICE_NAME.log`` to the latest log file.
 # Logs are kept for as long specified in ``LOGDAYS``.
+# This is deprecated....logs go in ``LOGDIR``, only symlinks will be here now.
 if [[ -n "$SCREEN_LOGDIR" ]]; then
 
     # We make sure the directory is created.