Fix goodreads custom shelf bug

[akhil-rasheed]

Closes #8158

Fixes the bug wherein an unchecked or custom shelved book causes the entire import to fail

Technical

Replaced 'return false' in the unchecked or custom shelf condition with a 'return'. This statement was causing the code to break out of the loop entirely when the condition was encountered

Testing

1. Go to ... import options.
2. Do ... try to import Goodreads data containing a custom exclusive shelf, or an unchecked book
   The bug should be fixed, and the import completes with error messages

Screenshot

Stakeholders

@jimchamp

[codecov-commenter]

Codecov Report

Merging #8306 (3a0856c) into master (586466c) will decrease coverage by 0.01%.
Report is 40 commits behind head on master.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #8306      +/-   ##
==========================================
- Coverage   16.99%   16.99%   -0.01%     
==========================================
  Files          75       75              
  Lines        3942     3943       +1     
  Branches      674      674              
==========================================
  Hits          670      670              
- Misses       2842     2843       +1     
  Partials      430      430              

Files	Coverage Δ
...library/plugins/openlibrary/js/goodreads_import.js	0.00% <0.00%> (ø)

[jimchamp]

Thanks @akhil-rasheed! This seems to be working as expected.

[jimchamp]

While reviewing this, I noticed that all best-fit ISBN to OLID matching is happening via client-side calls. If we do these checks server-side, before page load, we can likely avoid having any client-side code for this feature.