chore: Use --no-cache-dir flag to pip in Dockerfiles, to save space

Using "--no-cache-dir" flag in pip install ,make sure dowloaded packages
by pip don't cached on system . This is a best practise which make sure
to fetch ftom repo instead of using local cached one . Further , in case
of Docker Containers , by restricing caching , we can reduce image size.
In term of stats , it depends upon the number of python packages
multiplied by their respective size . e.g for heavy packages with a lot
of dependencies it reduce a lot by don't caching pip packages.

Further , more detail information can be found at

https://medium.com/sciforce/strategies-of-docker-images-optimization-2ca9cc5719b6

Signed-off-by: Pratik Raj <rajpratik71@gmail.com>

graphite/Dockerfile

@@ -24,12 +24,12 @@ RUN set -xe \
                python3 \
                python3-dev \
     && curl -sSL https://bootstrap.pypa.io/get-pip.py | python3 \
-    && pip3 install gunicorn supervisor \
-    && pip3 install --install-option=--prefix=/opt/graphite \
+    && pip3 install --no-cache-dir gunicorn supervisor \
+    && pip3 install --no-cache-dir --install-option=--prefix=/opt/graphite \
                     --install-option=--install-lib=/opt/graphite/lib \
                     whisper==$GRAPHITE_VERSION \
                     carbon==$GRAPHITE_VERSION \
-    && pip3 install --install-option=--prefix=/opt/graphite \
+    && pip3 install --no-cache-dir --install-option=--prefix=/opt/graphite \
                     --install-option=--install-lib=/opt/graphite/webapp \
                     graphite-web==$GRAPHITE_VERSION \
     && cd ./webapp \