[feat] Add configuration option to disable the ReqNodeNotAvail check

[vkarak]

Fixes #1049.

FYI @bcfriesen you can now either export RFM_IGNORE_REQNODENOTAVAIL=yes or set the ignore_reqnodenotavail configuration parameter to True.

[bcfriesen]

Great! Thanks @vkarak. I'll test this this week.

[codecov-commenter]

Codecov Report

Merging #1342 into master will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master    #1342   +/-   ##
=======================================
  Coverage   91.65%   91.65%           
=======================================
  Files          83       83           
  Lines       12595    12599    +4     
=======================================
+ Hits        11544    11548    +4     
  Misses       1051     1051           

Impacted Files	Coverage Δ
reframe/core/schedulers/slurm.py	56.11% <100.00%> (+0.39%)	⬆️
reframe/frontend/cli.py	77.64% <100.00%> (+0.06%)	⬆️

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[vkarak]

@bcfriesen Did you have time to test this one? If not, since it'd require you to move to 3.0 right away essentially, I could merge it anyway and if you see problems we can fix them in a later PR.

[bcfriesen]

Hi @vkarak, no I'm still migrating to the 3.0 series. Please feel free to merge this and I'll open an issue if it doesn't work as expected. Thanks!