Update docker files for 8_x

[dheles]

Description

Fixes reference to latest in docker files (since 8_x is no longer latest)

Instructions for Reviewers

Follow the instructions here:
https://wiki.lyrasis.org/display/DSPACE/Testing+DSpace+Github+Pull+Requests
to stand up a copy of the DSpace backend using docker. Check to make sure it's using the latest 8_x version.

List of changes in this PR:

• updated docker files to match their 7_x counterparts

Checklist

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[tdonohue]

👍 Thanks @dheles for catching this. This all looks correct, and the tests pass (which means it's working / building fine)