Optimised Django installation

With version 2.5.11 Netbox moved to Django 2.2 but the Dockerfile
stilled pulled 2.1.x in. With this change the requirements from Netbox
are installed first. So we have the correct version of Django installed
and the additional software can use is directly

Dockerfile

@@ -15,20 +15,6 @@ RUN apk add --no-cache \
       ttf-ubuntu-font-family \
       wget
 
-RUN pip install \
-# gunicorn is used for launching netbox
-      gunicorn \
-# napalm is used for gathering information from network devices
-      napalm \
-# ruamel is used in startup_scripts
-      ruamel.yaml \
-# pinning django to the version required by netbox
-# adding it here, to install the correct version of
-# django-rq
-      'Django>=2.1.5,<2.2' \
-# django-rq is used for webhooks
-      django-rq
-
 WORKDIR /opt
 
 ARG BRANCH=master
@@ -39,6 +25,16 @@ RUN wget -q -O - "${URL}" | tar xz \
 WORKDIR /opt/netbox
 RUN pip install -r requirements.txt
 
+RUN pip install \
+# gunicorn is used for launching netbox
+      gunicorn \
+# napalm is used for gathering information from network devices
+      napalm \
+# ruamel is used in startup_scripts
+      ruamel.yaml \
+# django-rq is used for webhooks
+      django-rq
+
 COPY docker/configuration.docker.py /opt/netbox/netbox/netbox/configuration.py
 COPY configuration/gunicorn_config.py /etc/netbox/config/
 COPY docker/nginx.conf /etc/netbox-nginx/nginx.conf