Merge branch 'rnou/163-dataclay-integration' into 'main'

Resolve "Root issues and stage-out with SPANK"

At the end, stage-out in root installation was never implemented, so this merge request does it:
1. Stage-in (and waiting until copy happens, bool in trasfer_datasets)
2. Stage-out (and waiting until copy happens)
3. terminates adhoc fs
4. removes adhoc fs directory.

Some issues with needed environment variables solved, however LIBGKFS_HOSTS_FILE and GKFS_DAEMON and GKFS_CLIENT should be defined in the environment as they are installation dependant.

See merge request !126