Support user-supplied db port for startup check

Author: thespad

root/etc/cont-init.d/50-config

@@ -99,7 +99,7 @@ fi
 echo "Waiting for DB to be available"
 END=$((SECONDS+30))
 while [[ ${SECONDS} -lt ${END} ]] && [[ -n "${DB_HOST+x}" ]]; do
-    if [[ $(/usr/bin/nc -w1 "${DB_HOST}" 3306 | tr -d '\0') ]]; then
+    if [[ $(/usr/bin/nc -w1 "${DB_HOST}" "${DB_PORT}" | tr -d '\0') ]]; then
         if [[ -n "${RUN}" ]]; then
             break
         fi