hashunittest: run sha384longtest only for providers that support sha384
hashunittest: run sha384longtest only for providers that support sha384

Fixes commit bdb0e9d37d78ec8e01d4008dba5243afe9029346 that accidentally
left the wrong logic when refactoring the file, and makes the check as
done in the other longtest tests.

KDE/qca,KDE/qca,KDE/qca,KDE/qca