Bug 1841: LTS Support

Updates base to Ubuntu 20.04
Updates python to 3.8
Updates pip dependencies to more recent versions
Adds apt cache to stage 2 dockerfile

Fixes bug 1841

Change-Id: I70af3cfab7484d7b284c143d554bef9f0be51812
Signed-off-by: beierlm <mark.beierl@canonical.com>
diff --git a/docker/MON/Dockerfile b/docker/MON/Dockerfile
index adb736a..281e039 100644
--- a/docker/MON/Dockerfile
+++ b/docker/MON/Dockerfile
@@ -25,13 +25,15 @@
 
 RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
     DEBIAN_FRONTEND=noninteractive apt-get --yes install \
-    curl=7.68.* \
     gcc=4:9.3.* \
     python3=3.8.* \
-    python3-setuptools=45.2.* \
     python3-dev=3.8.* \
-    openssh-client=1:8.* && \
-    python3 -m easy_install pip==21.0.1 setuptools==51.0.0
+    python3-pip=20.0.2* \
+    python3-setuptools=45.2.* \
+    curl=7.68.*
+
+RUN DEBIAN_FRONTEND=noninteractive apt-get --yes install \
+    openssh-client=1:8.*
 
 ARG PYTHON3_OSM_COMMON_URL
 ARG PYTHON3_OSM_MON_URL
@@ -51,11 +53,22 @@
     -r /usr/lib/python3/dist-packages/osm_common/requirements.txt \
     -r /usr/lib/python3/dist-packages/osm_mon/requirements.txt
 
+#######################################################################################
 FROM ubuntu:20.04 as FINAL
 
+ARG APT_PROXY
+RUN if [ ! -z $APT_PROXY ] ; then \
+    echo "Acquire::http::Proxy \"$APT_PROXY\";" > /etc/apt/apt.conf.d/proxy.conf ;\
+    echo "Acquire::https::Proxy \"$APT_PROXY\";" >> /etc/apt/apt.conf.d/proxy.conf ;\
+    fi
+
 RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
     DEBIAN_FRONTEND=noninteractive apt-get --yes install \
     python3-minimal=3.8.* \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN DEBIAN_FRONTEND=noninteractive apt-get --yes update && \
+    DEBIAN_FRONTEND=noninteractive apt-get --yes install \
     ca-certificates \
     && rm -rf /var/lib/apt/lists/*