Set server URL to EOSC VM

[stefanos1316]

Changed the server URL where the devices are fetching the update.sh and filter.sh. Now, the devices will use the https://epidose.ellak.gr. Here is the output from the current test:

2021-04-20 09:26:47 Killed during sleep; obtaining a new filter
2021-04-20 09:26:47 Obtaining new filter from https://epidose.ellak.gr/
2021-04-20 09:26:47 Acquiring WiFi
2021-04-20 09:26:47 Turn on WiFi
2021-04-20 09:26:47 Temporary stop beacon transmissions
2021-04-20 09:26:49 Acquired WiFi
2021-04-20 09:26:49 Checking for updates
2021-04-20 09:26:50 New update script obtained: 188 bytes
2021-04-20 09:27:51 New filter obtained: 188 bytes 

As said, the server will generate a new filter every six hours by invoking the following cronjob:

0 */6 * * * /home/sgeorgiou/epidose/venv/bin/python /home/sgeorgiou/epidose/epidose/back_end/create_filter.py -v -d /var/lib/epidose/filter.bin

I have used the /home/sgeorgiou since this account was created for me by ELLAK. If you like to, I can create another root account named epidose that we share between us.

Also, I will issue another PR to generate the above cronjob through the deploy.yml script of the back_end.

[dspinellis]

Please also adjust the README file

[stefanos1316]

Sure, will adjust it now.

[stefanos1316]

@dspinellis I guess you mean that I should remove unnecessary text like the following: "After downloading the project you can run the health authority server code on a (hopefully) more powerful Raspberry-Pi host as follows."

Please note that there are instructions on how to run the deploy.yml in the README.md file.

I can also write the requirements, for instance, update.sh file should be in this folder in order to run the server. This is what you meant by the adjust?

[dspinellis]

Ah, OK. If we already have instructions for deploying on a server no adjustment is needed.

[stefanos1316]

Still, I have made a few in this PR to clarify some things.