Fix job matching without explicit Identifier keyword.

[ArneBab]

if identifier is not given explicitly in the options, we need to add it to ensure that the replies find matching jobs.

This makes node.refstats() work again.

[Thynix]

In my testing (through the test-autograde script) it doesn't appear broken. Are you sure this is broken on master?

[ArneBab]

It was broken for me, but I did quite some internal meddling in my branches which might have broken stuff…

[ArneBab]

closing: changes already includen