Correct dotnet entrypoint script to run the function host as the main process

[AlexPykavy]

To ensure the signals are sent to the function host process rather than the entrypoint itself. For more details, see https://medium.com/@leonardo5621_66451/learn-how-to-use-entrypoint-scripts-in-docker-images-fede010f172d

Before:

root           1  0.0  0.0   3896  2788 ?        Ss   11:46   0:00 bash /opt/startup/start_nonappservice.sh
root           9 17.3  2.3 23691108 185812 ?     Sl   11:46   0:06 /azure-functions-host/Microsoft.Azure.WebJobs.Script.WebHost
root          36  2.8  0.6 3680016 51824 ?       Sl   11:46   0:00 dotnet /app/App.dll --host 127.0.0.1 --port 43181 --workerId d1ce5a9f-ae39-41
...

Now:

USER         PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root           1  7.3  2.3 23469624 184548 ?     Ssl  11:49   0:02 /azure-functions-host/Microsoft.Azure.WebJobs.Script.WebHost
root          35  1.8  0.6 3802876 52540 ?       Sl   11:49   0:00 dotnet /app/App.dll --host 127.0.0.1 --port 42789 --workerId a39ebb64-de06-49
...

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