Prepare was failing in client_ar.sh because of a typo in KrB5CCNAME, adding -s to prepare as by xrootd definition we are staging files to disk and not discovering them.

moment and won't be used in production (egroups).

Must add prepare acl on /eos/ctaeos/cta folder so that the retrieve works for the first test (may not be useful...)

Removed castor-rmc-server rpm from buildtree-stage1-rpms/Dockerfile because CTA now builds /usr/bin/cta-rmcd

Forwarding -b and -B options to `create_instance.sh` so that we can run the buildtree test directly like this:
```
./run_systemtest.sh  -n toto -s tests/archive_retrieve.sh -O -D -k -b /buildtree -B CTA-build
```
This will be very helpful to test buildtree in CI automatically.

As systemd is mounting tmpfs in /tmp, I had to move the artifacts
repository to /opt/repo (which is anyway better).
Default entry point in the container is systemd and I added /etc/rc.local entry point for systemd containers.
Initially it is pulled from a shared mount on the kubelet running the
pod.
This commit is compatible with the standard way of running CI jobs,
following sytemd commits may break retrocompatibility.

Default ctafrontend rpm xrootd configuration file is CI ready. No more duplicate in the continuousintegration tree.

Changing /etc/ctafrontend_SSS_c.keytab and /etc/ctafrontend_SSS_s.keytab to /etc/cta/cta-cli.sss.keytab so that CI and preprod have now the same configuration files.

Keep in mind thatL
The user in the ctafrontend SSS key is the EOS instance name, the rest is BS. I tried to make it clear in the configuration files and names when a field is useless.
WFE scripts are now the same between preprod and CI and the ctafrontend
configuration file can move in the rpm.

Using /etc/cta/cta-frontend.krb5.keytab file as ctafrontend kerberos keytab instead of /etc/cta-frontend.krb5.keytab

moving ctafrontend xrootd configuration file from /etc/xrootd/xrootd-cta.cfg to /etc/cta/cta-frontend-xrootd.conf

Fixing the fluctuations in the archived file count that are due to the automatic deletion of disk replicas in the workflow.

Removing cta frontend and xrootd logs from stdout of the pod as kubectl logs is broken and only displays partial logs. xrootd logs are now going in /var/log/cta-frontend-xrootd.log to be collected later in the varlog archive as artifacts.

Compiles without XRDSSI_DEBUG and removes --json option from scripts