fts is tagged inconsistently with other containers

[maxnoe]

The fts tags on docker hub are missing the release- prefix, that is common to all other containers.

I.e. compare:

https://hub.docker.com/r/rucio/rucio-server/tags?page=1&name=34.0.0

to

https://hub.docker.com/r/rucio/fts/tags?page=1&name=34.0.0

[bari12]

We should think about why we version these (fts, xrootd, etc.) anyway - do we need it?

[bjwhite-fnal]

In particular, since you said et cetera, I'd like to make sure we keep version tags on the fts-cron container at least.