Pin libjuju version to 2.8.2

Fixes bug 1144

Change-Id: Ib50f76e45b9d429f019972c367b6692ed2d5ed79
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>
(cherry picked from commit 2ed0e235)

docker/MON/Dockerfile

@@ -61,7 +61,7 @@ RUN curl ${REPOSITORY_BASE}/${RELEASE}/${REPOSITORY_KEY} | apt-key add - \
                           python3-n2vc${N2VC_VERSION}
 
 
-RUN python3 -m pip install -U "juju==2.8.1"
+RUN python3 -m pip install -U "juju==2.8.2"
 
 COPY scripts/ scripts/