Create dokku's /var/log/dokku/ private namespace

Rename dokku.log to events.log.
Refresh tests accordingly.

plugins/20_events/install

@@ -7,6 +7,11 @@ DOKKU_LOGROTATE_FILE=/etc/logrotate.d/dokku
 
 flag_rsyslog_needs_restart=n
 
+# This can be done unconditionally as mkdir -p
+# exits gracefully if the path already exists
+mkdir -m 775 -p "$DOKKU_LOGS_DIR"
+chown syslog:dokku "$DOKKU_LOGS_DIR"
+
 if [[ ! -f  "$DOKKU_EVENTS_LOGFILE" ]]; then
   touch "$DOKKU_EVENTS_LOGFILE"
   # chown syslog:root might not work on SUSE
@@ -23,7 +28,7 @@ fi
 
 if [[ ! -f "$DOKKU_LOGROTATE_FILE" ]]; then
   cat >"$DOKKU_LOGROTATE_FILE" <<EOF
-$DOKKU_EVENTS_LOGFILE {
+$DOKKU_LOGS_DIR/*.log {
         daily
         rotate 7
         missingok