Upgrading PyYaml due to new juju package - MON devops dockerfile

Change-Id: Id8575b8378c15f2faa59a3971d3db3a58f9b89f5
Signed-off-by: lavado <glavado@whitestack.com>

docker/MON/Dockerfile

@@ -41,7 +41,7 @@ RUN apt-get update \
     && pip3 install pip==9.0.3
 
 RUN pip3 install  'macaroonbakery>=1.1,<2.0' 'pyRFC3339>=1.0,<2.0' \
-      'pyyaml>=3.0,<4.0' 'theblues>=0.3.8,<1.0' 'websockets>=4.0,<5.0' \
+      'pyyaml>=5.1.2' 'theblues>=0.3.8,<1.0' 'websockets>=4.0,<5.0' \
       'paramiko'   # PyNaCl
 
 ARG REPOSITORY_BASE=http://osm-download.etsi.org/repository/osm/debian