Test that +short does not leak the ";; " comments

Test that +short does not leak the ";; " comments

Plain +short already turns lookup->comments off, so the regression it
guards against only surfaces with "+short +comments", where +comments
re-enables the comment toggle while short form is still in effect.  The
existing silent-then-servfail scenario is reused because its retry path
reliably prints a "Got SERVFAIL reply from ..." comment; the +comments
case (without +short) is asserted first so the absence check is
meaningful.

Assisted-by: Claude:claude-opus-4-8