RFR: 8310874: Runthese30m crashes with klass should be in the placeholders during verification

[Coleen Phillimore]

For non-parallel capable class loaders, the class is not put in the placeholders table, so a verification at the wrong time will hit this assert. This change removes the invalid assert.
While studying this code, we also noticed that if an error occurs during class loading after the klass is put in the LoaderConstraints table but before adding to the dictionary, we weren't removing the klass from the LoaderConstraints table.  This change also fixes this.
Tested with inserting a LoaderConstraintTable::verify while running jck tests.  Also tested with failure insertion after the addClass() call to throw OutOfMemoryError.  Also tested with tier1-4.

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Commit messages:
 - Remove klass from loader constraint table if an error occurs during loading.
 - 8310874: Runthese30m crashes with klass should be in the placeholders during verification

Changes: https://git.openjdk.org/jdk/pull/15752/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15752&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310874
  Stats: 31 lines in 3 files changed: 17 ins; 11 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/15752.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15752/head:pull/15752

PR: https://git.openjdk.org/jdk/pull/15752