Move dependency installation to Dockerfile

Moved installation of speedtest commandline utility to Dockerfile.
Did not remove the (optional, if no cmdline utility found) installation
from entrypoint, so that the program can be run from entrypoint without
using docker as a fall-back.

Dockerfile

@@ -1,6 +1,6 @@
 FROM python:3.8-slim-buster
-LABEL maintainer="Breadlysm" \
-    description="Original by Aiden Gilmartin. Maintained by Breadlysm"
+LABEL maintainer="Marty Oehme" \
+    description="Original by Aiden Gilmartin & Breadlysm."
 
 ENV DEBIAN_FRONTEND=noninteractive
 
@@ -10,6 +10,12 @@ RUN true &&\
 apt-get update && \
 apt-get -q -y install --no-install-recommends apt-utils gnupg1 apt-transport-https dirmngr && \
 \
+# Add repos
+apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 379CE192D401AB61 && \
+echo "deb https://ookla.bintray.com/debian buster main" > /etc/apt/sources.list.d/speedtest.list && \
+apt-get update && \
+apt-get -q -y install --no-install-recommends speedtest && \
+\
 # Install Python packages
 pip3 install pythonping influxdb-client && \
 \

entrypoint.sh

@@ -1,11 +1,10 @@
 #!/bin/sh
 
 printenv >>/etc/environment
-ln -snf /usr/share/zoneinfo/$TZ /etc/localtime && echo $TZ > /etc/timezone
+ln -snf "/usr/share/zoneinfo/$TZ" /etc/localtime && echo "$TZ" >/etc/timezone
 
 # Install speedtest-cli
-if [ ! -e /usr/bin/speedtest ]
-then
+if [ ! -e /usr/bin/speedtest ]; then
     apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 379CE192D401AB61
     echo "deb https://ookla.bintray.com/debian buster main" | tee /etc/apt/sources.list.d/speedtest.list
     apt-get update && apt-get -q -y install speedtest
@@ -13,4 +12,4 @@ then
     rm -rf /var/lib/apt/lists/*
 fi
 
-exec /usr/local/bin/python3 $@
+exec /usr/local/bin/python3 "$@"