fix init reordering bug

[ankona]

Fix 3 bugs:

1. reordering the init sequence in the dragon backend resulted in an un-set collection being used
2. fix tests that should have been updated to compare set contents instead of individual items
3. remove newly added validation on empty host lists that broke existing tests

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Please upload report for BASE (mli-feature@ef034d5). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
smartsim/_core/launcher/dragon/dragonBackend.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             mli-feature     #675   +/-   ##
==============================================
  Coverage               ?   79.26%           
==============================================
  Files                  ?       98           
  Lines                  ?     7910           
  Branches               ?        0           
==============================================
  Hits                   ?     6270           
  Misses                 ?     1640           
  Partials               ?        0           

Files with missing lines	Coverage Δ
smartsim/_core/launcher/dragon/pqueue.py	90.42% <ø> (ø)
smartsim/_core/launcher/dragon/dragonBackend.py	1.96% <0.00%> (ø)

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[al-rigazzi]

LGTM, thanks for this fix!