Close a small memory leak when stage initialization fails

[cottsay]

Ownership of cmd_ctx doesn't get transferred to ctx until 5 lines later, so we need to explicitly free it during failure handling here.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 54.60%. Comparing base (488c204) to head (a32177c).

Files with missing lines	Patch %	Lines
src/createrepo-agent/command.c	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #49      +/-   ##
==========================================
- Coverage   54.64%   54.60%   -0.04%     
==========================================
  Files          22       22              
  Lines        2853     2855       +2     
  Branches      598      599       +1     
==========================================
  Hits         1559     1559              
- Misses        974      975       +1     
- Partials      320      321       +1     

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