Fix/fdb 541 root trailing slash

[ChrisspyB]

Description

Fixes #162 , unable to list roots configured with a trailing slash.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/dev-section/fdb/pull-requests/PR-164

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.27%. Comparing base (4ea8e64) to head (8d8aeca).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #164      +/-   ##
===========================================
- Coverage    74.28%   74.27%   -0.01%     
===========================================
  Files          331      331              
  Lines        20270    20272       +2     
  Branches      2094     2094              
===========================================
  Hits         15058    15058              
- Misses        5212     5214       +2     

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[ChrisspyB]

Failing remoteFDB test is unrelated.