Remove gulp install and set npm version to 7 in the .Dockerimage (#815)

The NPM 8 is returning 1 from some commands which were working without issues in NPM 7.

Author: bigmontz

testkit/Dockerfile

@@ -13,9 +13,8 @@ RUN apt-get update && \
         firefox \
     && rm -rf /var/lib/apt/lists/*
 
-RUN npm install -g npm \
+RUN npm install -g npm@7 \
     && /bin/bash -c "hash -d npm"
-RUN npm install -g gulp
 
 # Enable tls v1.0
 RUN echo "openssl_conf = openssl_configuration\n"|cat - /etc/ssl/openssl.cnf > /tmp/openssl_conf.cnf \  
@@ -40,4 +39,4 @@ USER driver
 WORKDIR /home/driver
 CMD /bin/bash
 RUN mkdir /home/driver/.npm_global
-RUN npm config set prefix /home/driver/.npm_global
+RUN npm config set prefix /home/driver/.npm_global