Tweak EPICS backend record initialisation logic

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 43.86%. Comparing base (f887045) to head (9ae4f7a).

Files	Patch %	Lines
src/fastcs/backends/epics/ioc.py	0.00%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## adopt-copier-template #29 +/- ## ====================================================== Coverage 43.86% 43.86% ====================================================== Files 18 18 Lines 652 652 ====================================================== Hits 286 286 Misses 366 366 ```

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