BUGFIX: Delete related tags during flush
BUGFIX: Delete related tags during flush

This prevents getting non existent identifiers when
calling `findIdentifiersByTag`.

kdambekalns/flow-development-collection,robertlemke/flow-development-collection,neos/flow-development-collection,neos/flow-development-collection,fcool/flow-development-collection,fcool/flow-development-collection,neos/flow-development-collection,robertlemke/flow-development-collection,robertlemke/flow-development-collection,kdambekalns/flow-development-collection,kdambekalns/flow-development-collection,kdambekalns/flow-development-collection,neos/flow-development-collection,robertlemke/flow-development-collection,fcool/flow-development-collection,fcool/flow-development-collection