Translate CasMismatchException to OptimisticLockingFailureException.

[mikereiche]

Translate CasMismatchException to OptimisticLockingFailureException
instead of DataIntegrityViolationException. CasMismatchException is
a ConcurrencyFailureException which is a TransientDataAccessException.
Versus DataIntegrityViolation, which is a NonTransientDataAccessException.

Closes #1339.

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