Bug fix for box2001: aiu now multiplies the air stress components

[JFLemieux73]

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PR checklist

• Short (1 sentence) summary of your PR:
  air stress components are now correctly multiplied by ice concentration at the u point (aiu) for box2001 experiment.
• Developer(s):
  @JFLemieux73
• Suggest PR reviewers from list in the column to the right. @eclare108213 @TillRasmussen
• Please copy the PR test results link or provide a summary of testing completed below.
  All the tests are bfb except (or course) box2001.
• How much do the PR code changes differ from the unmodified code?
  • bit for bit (except for box2001)
  • different at roundoff level
  • more substantial
• Does this PR create or have dependencies on Icepack or any other models?
  • Yes
  • No
• Does this PR add any new test cases?
  • Yes
  • No
• Is the documentation being updated? ("Documentation" includes information on the wiki or in the .rst files from doc/source/, which are used to create the online technical docs at https://readthedocs.org/projects/cice-consortium-cice/. A test build of the technical docs will be performed as part of the PR testing.)
  • Yes
  • No, does the documentation need to be updated at a later time?
    • Yes
    • No
• Please provide any additional information or relevant details below:

[TillRasmussen]

Approved