add if;then;fi

docker-entrypoint.sh

@@ -1,12 +1,13 @@
 #!/usr/bin/env bash
-
-echo "Initial nslookup ${HOSTNAME}.${APPNET}"
-nslookup ${HOSTNAME}.${APPNET}
-while [ $? -ne 0 ]; do
-  echo "Waiting for ${HOSTNAME}.${APPNET} to become available"
-  sleep 1
-  nslookup ${HOSTNAME}.${APPNET}
-done
+if [ ! -z "${APPNET}" ]; then
+   echo "Initial nslookup ${HOSTNAME}.${APPNET}"
+   nslookup ${HOSTNAME}.${APPNET}
+   while [ $? -ne 0 ]; do
+     echo "Waiting for ${HOSTNAME}.${APPNET} to become available"
+     sleep 1
+     nslookup ${HOSTNAME}.${APPNET}
+   done
+fi
 
 /opt/updatedb.sh