Enable testing of high availability data transfer nodes for SRC Net 0.1

BH: A highly resilient and performant DTN Endpoint will allow for production-level performance to be demonstrated, and for further optimisation and prototyping work to be developed against.

For SRCNet - "provides an endpoint that could be tested in anger", provides stable endpoints for receiving data.

Must haves for UK:

AC1: At least two DTN hosts are installed and provisioned

AC2: Functional transfers between other demonstrator endpoints have been performed, using appropriate token-based authorisation and orchestrated data movement. In particular in connection with the Rucio testbed.

Must have for SRCNet... but not urgent for this PI:

Stretch: Documentation and recipies for other sites - is made available

(Stretch, not needed for 0.1): A High Availability (clustered) setup is configured and demonstrated

Moving to releasing, due to the completion of the two AC.

AC1: One XRootD server is installed and provisioned (and participating in functional tests within Rucio). 
The additional XRootD servers are physically installed, but awaiting final network routing configuration and installation of software. 
The single XRootD instance has already demonstrated ~ 50Gb/s throughput, and ~ 10Gb/s transfers from another SRCNet Node site. 

AC2: Demonstration of successful transfer to the XRootD can be seen at: https://monit.srcdev.skao.int/grafana/d/BfW0IQQVk/rucio-events?orgId=1&var-src=All&var-dst=UKSRC_RAL_XRD_DEVCEPHFS&var-protocol=All&var-scopes=testing&var-filename=%2A&var-bin=$__auto_interval_bin&var-throughput_min_filesize_bytes=1000000&from=now-30d&to=now

Initially identified stretch activities will be picked up next PI.