fix: mapnode to generate result file when crashes in single node mode

[satra]

Summary

Fixes #3088

List of changes proposed in this PR (pull-request)

Allows MapNodes that have one subnode to generate a results file before erroring out

Acknowledgment

• (Mandatory) I acknowledge that this contribution will be available under the Apache 2 license.

[satra]

@effigies - if this works for you as well, we should add a hotfix to 1.3.x

[codecov]

Codecov Report

Merging #3143 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3143      +/-   ##
==========================================
+ Coverage   67.59%   67.59%   +<.01%     
==========================================
  Files         299      299              
  Lines       39480    39487       +7     
  Branches     5220     5220              
==========================================
+ Hits        26685    26690       +5     
- Misses      12082    12085       +3     
+ Partials      713      712       -1

Flag	Coverage Δ
#smoketests	53.02% <55.55%> (-0.01%)	⬇️
#unittests	64.86% <100%> (+0.02%)	⬆️

Impacted Files	Coverage Δ
nipype/pipeline/engine/nodes.py	83.49% <100%> (+0.18%)	⬆️
nipype/info.py	93.84% <100%> (ø)	⬆️
nipype/pipeline/plugins/tools.py	78.94% <0%> (-1.32%)	⬇️
nipype/pipeline/engine/utils.py	80.5% <0%> (-0.12%)	⬇️

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[effigies]

@satra This fixes #3088 for me. Want me to cherry-pick a new PR for maint/1.3.x, or is that easier for you to do?

Edit: Cherry-picked to test that 1.3.x + this fix resolves the issue as well. Opened #3144.

[effigies]

Also, could you rebase this to maint/1.4.x? master is currently set to 1.5.0-dev.

Cancel that. Looks like we've been pushing to master, so there's no point. This is good to merge.