Qt4Project: Only complain about missing subdirs from the exact parse

Task-number: QTCREATORBUG-8941

Change-Id: Ie843529e42ede29d607932d5fbd9e92da2fd8082
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Daniel Teske <daniel.teske@digia.com>