inv: Correct Docker marist s390x node name

[Willsparker]

ref: #1716 (comment)

• inventory changes, ensure bastillion is updated accordingly

Just some mistakes I noticed whilst going through the list of machines that need to be added to Nagios. As these are inconsistent with the node names in Jenkins, my Nagios check (#1717) is unable to find them. I opted for changing the inventory entry as this is easier than renaming the node in Jenkins :-)

[sxa]

this change to add the l onto a subset of the arm systems makes the naming inconsistent as many are still left as armv8 / armv7, so I would suggest we need to change the definitions elsewhere.

[Willsparker]

I'll take that out - we should probably change it in Jenkins then :-)

[karianna]

lgtm