add package upgrade and dedicated user to dockerfile

Dockerfile

@@ -3,10 +3,13 @@ WORKDIR /app
 ADD ./app/requirements.txt .
 RUN pip install -r /app/requirements.txt
 RUN apt-get update && \
+    apt-get -y upgrade && \
     apt-get -y install \
       monitoring-plugins \
       monitoring-plugins-contrib && \
     apt-get clean
 
+RUN useradd monitoring -m
+
 ADD ./app .
-USER daemon
+USER monitoring