Update to checkAppClassAndResourceAccess

[jimblye]

• I have considered the risk of behavior change or other zero migration impact (https://github.com/OpenLiberty/open-liberty/wiki/Behavior-Changes).
• If this PR fixes an Issue, the description includes "Fixes #FILLMEIN" or "Resolves #FILLMEIN" (verify release bug label if applicable: https://github.com/OpenLiberty/open-liberty/wiki/Open-Liberty-Conventions).
• If this PR resolves an external Known Issue (including APARS), the description includes "Fixes #FILLMEIN" or "Resolves #FILLMEIN".

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Test fix:

• Before the fix, the negative resource requests sent resosurcename=...
• The servlet never reads that parameter, because it only looks for "resourcename"
• Therefore resourcename == null
• Then the entire resource-check block is skipped:
  no getClass().getResource(...)
  no validation of expected failure
  no servlet exception if the resource is unexpectedly visible
• The request would return successfully unless some unrelated failure occurred

[jimblye]

!buiild

[jimblye]

!build (view Open Liberty Personal Build - ✅ completed successfully!)

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[LibbyBot]

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