re-add kubectl

Dockerfile

@@ -8,11 +8,12 @@ ENV DEBIAN_FRONTEND=noninteractive
 COPY SWITCHaai-swdistrib.gpg kubernetes-archive-keyring.gpg /usr/share/keyrings/
 
 # ca-certificates is required to access the kubernetes repo, thus the double dip
-RUN echo "deb [signed-by=/usr/share/keyrings/SWITCHaai-swdistrib.gpg] http://pkg.switch.ch/switchaai/ubuntu focal main" > /etc/apt/sources.list.d/SWITCHaai-swdistrib.list && \
-    apt-get update && \
+RUN apt-get update && \
     apt-get install -y --no-install-recommends ca-certificates && \
+    echo "deb [signed-by=/usr/share/keyrings/SWITCHaai-swdistrib.gpg] http://pkg.switch.ch/switchaai/ubuntu focal main" > /etc/apt/sources.list.d/SWITCHaai-swdistrib.list && \
+    echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" > /etc/apt/sources.list.d/kubernetes.list && \
     apt-get update && \
-    apt-get install -y --no-install-recommends apache2 shibboleth libapache2-mod-shib openssl && \
+    apt-get install -y --no-install-recommends apache2 shibboleth libapache2-mod-shib openssl kubectl && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/* && \
     rm -rf /etc/apache2/conf-available && \