Improve code coverage in hdmf common

[stephprince]

Motivation

Partially address #1323. Adds additional testing for code in hdmf common.

Checklist

• Did you update CHANGELOG.md with your changes?
• Does the PR clearly describe the problem and the solution?
• Have you reviewed our Contributing Guide?
• Does the PR use "Fix #XXX" notation to tell GitHub to close the relevant issue numbered XXX when the PR is merged?

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 92.26%. Comparing base (886bf4a) to head (8729205).

Files with missing lines	Patch %	Lines
src/hdmf/common/table.py	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1330      +/-   ##
==========================================
+ Coverage   91.62%   92.26%   +0.63%     
==========================================
  Files          42       42              
  Lines        9684     9677       -7     
  Branches     1963     1962       -1     
==========================================
+ Hits         8873     8928      +55     
+ Misses        523      471      -52     
+ Partials      288      278      -10     

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