fix nordvpn ping issue (#260)

Fixing #240  by re-using the existing environmental variable in this script as well

openvpn/nordvpn/configure-openvpn.sh

@@ -192,7 +192,13 @@ download_hostname() {
 }
 
 checkDNS() {
-  res=$(dig +short ${nordvpn_dl})
+  if [ -z "${HEALTH_CHECK_HOST}" ]; then
+    checkServer=${nordvpn_dl}
+  else
+    checkServer=${HEALTH_CHECK_HOST}
+    log "Checking DNS using server ${checkServer}"
+  fi
+  res=$(dig +short ${checkServer})
   if [ -z "${res:-\"\"}" ]; then
     log "DNS: ERROR, no dns resolution, dns server unavailable or network problem"
   else
@@ -201,9 +207,9 @@ checkDNS() {
   ping -c2 ${nordvpn_dl} 2>&1 >/dev/null
   ret=$?
   if [ $ret -eq 0 ]; then
-    log "PING: ok, configurations download site reachable"
+    log "PING: ok"
   else
-    log "PING: ERROR: cannot ping ${nordvpn_cdn}, network or internet unavailable. Cannot download NORDVPN configuration files"
+    log "PING: ERROR: cannot ping ${checkServer}, network or internet unavailable. Cannot download NORDVPN configuration files"
   fi
   return $ret
 }