Backup/restore logic for required files

[andywaltlova]

Talked with @kokesak about the possible improvement of the c2r repo (required files) download logic.

Now the script does:

1. Setup (includes download of gpg key and repo files) - files are always downloaded, if they exist they are backed up
2. Check if convert2rhel is installed
3. Install/update of ocnvert2rhel pkg

Now this works nicely, but the issue we had about urlopen error got us thinking if we need to download them every time. Question here is if it does matter from where the convert2rhel package was installed on the system or do we care only about the fact that it is there? What would happen if it would be older version and because of wrong repo we wouldn't be able to update it?

This updated steps would work too, but it would introduce the possibility of failed update of convert2rhel pkg.

1. Check if convert2rhel is installed
2. Optional Setup (includes download of gpg key and repo files) - only if convert2rhel pkg is not installed
3. Install/update of convert2rhel pkg

Is there a legit use case where customer would already have the convert2rhel pkg fro mdifferent source and wouldn't have the possibility (or simply wouldn't want) to download our required files? (=the urlerror would block him)