reset loader folder after recursive defaults

[gerrfarr]

This fixes an issue that arrises when loading e.g. both params and priors via the !defaults constructor. The folder must be reset to the directory of the current yaml file so that the following paths can be interpreted relative to that

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.81%. Comparing base (5787446) to head (7fe20c1). Report is 1 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #360 +/- ## ========================================== - Coverage 81.82% 81.81% -0.01% ========================================== Files 146 146 Lines 11176 11177 +1 ========================================== Hits 9145 9145 - Misses 2031 2032 +1 ```

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