This reverts commit ebf7680f.

satisfy the FST ofs.tpc /usr/bin/xrdcp requirement. For further details
look at the comments in the commit.

- Auto-detect whether QDB and client containers exist
- Collect fuse(x) logs from the client containers

  - Install fewer packages as most of them should be brought as dependencies by EOS
  - Don't install xrootd packages. Again, these are EOS dependencies
  - Remove forwardable keytab commands. The "xrdsssadmin" tool is only avaible in the xrootd-server package, which shouldn't be installed for a client-only image
  - Set up proper permissions of the keytab: daemon:daemon owner, 600 mod

- Use repo files instead of printing the repository via echo command
- XRootD will be installed from the eos-depend repo
- The xrd_testing image will disable xrootd from eos-depend and install from the xrootd-testing repo

Images from Dockerfile will now have a forwardable keytab by default. This won't have backward compatibility implications.