Change Ubuntu Docker image to install XRootD latest release instead of latest master commit

Dockerfile_ubuntu_bionic

@@ -32,8 +32,8 @@ RUN apt-get install -y build-essential git gdebi-core \
 
 # Add XRootd repo
 RUN curl -sL http://storage-ci.web.cern.ch/storage-ci/storageci.key | apt-key add - && apt-get update
-RUN echo "deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic master\n# deb-src http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic master" >> /etc/apt/sources.list
-RUN add-apt-repository 'deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic master'
+RUN echo "deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release\n# deb-src http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release" >> /etc/apt/sources.list
+RUN add-apt-repository 'deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd bionic release'
 
 # Create local repo from eos artifacts
 ENV EOSREPODIR="/debs/eos/"

Dockerfile_ubuntu_disco

@@ -32,8 +32,8 @@ RUN apt-get install -y build-essential git gdebi-core \
 
 # Add XRootd repo
 RUN curl -sL http://storage-ci.web.cern.ch/storage-ci/storageci.key | apt-key add - && apt-get update
-RUN echo "deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco master\n# deb-src http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco master" >> /etc/apt/sources.list
-RUN add-apt-repository 'deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco master'
+RUN echo "deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco release\n# deb-src http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco release" >> /etc/apt/sources.list
+RUN add-apt-repository 'deb http://storage-ci.web.cern.ch/storage-ci/debian/xrootd disco release'
 
 # Create local repo from eos artifacts
 ENV EOSREPODIR="/debs/eos/"