Fix load of old moxa registry entries

[FreddieAkeroyd]

Fix loading of old moxa registry entries

See ISISComputingGroup/uktena#30

Code Review

• Is the code of an acceptable quality?
• Has the author taken into account the multi-threaded nature of the code?
• Have the changes been recorded appropriately in a PR for release notes?
• Has the manual system tests spreadsheet been updated?

Functional Tests

• Do changes function as described? Add comments below that describe the tests performed.

Final steps

• Reviewer has updated the submodule in the main EPICS repo? See Reviewing work for the subModules of EPICS in the Git workflow page for details.
• Reviewer has merged the associated PR for the release notes