openvidu-deployment: install dnsutils in openvidu-server, openvidu-server-pro and coturn to use dig

openvidu-server/docker/openvidu-coturn/Dockerfile

@@ -1,7 +1,7 @@
 FROM ubuntu:16.04
 
 RUN apt-get update \
-    && apt-get install -y coturn curl
+    && apt-get install -y coturn curl dnsutils
 
 COPY ./configuration-files.sh /tmp/
 COPY ./entrypoint.sh /usr/local/bin

openvidu-server/docker/openvidu-server-pro/Dockerfile

@@ -11,6 +11,7 @@ RUN apt-get update && apt-get install -y \
   jq \
   docker.io \
   ethtool \
+  dnsutils \
 && rm -rf /var/lib/apt/lists/*
     
 RUN mkdir -p /opt/openvidu /usr/local/bin/

openvidu-server/docker/openvidu-server/Dockerfile

@@ -8,6 +8,7 @@ RUN apt-get update && apt-get install -y \
   openjdk-8-jre \
   coturn \
   redis-tools \
+  dnsutils \
 && rm -rf /var/lib/apt/lists/*
 
 # Copy OpenVidu Server