fix: remove try from tests

[mcakircali]

Description

removes try() from shell tests as it creates sub-shell and returns true. one could add pipefail but it's prone to error. so, simply removed those and add -eux (e: exit, u:unset, x:print)

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 FDB 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/fdb/pull-requests/PR-271

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.86%. Comparing base (7c39511) to head (0c76e70).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #271      +/-   ##
===========================================
+ Coverage    70.72%   70.86%   +0.13%     
===========================================
  Files          372      372              
  Lines        23309    23309              
  Branches      2455     2454       -1     
===========================================
+ Hits         16486    16517      +31     
+ Misses        6823     6792      -31     

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