test suite: add more debugging output for notmuch-new

[David Bremner]

Tomi Ollila <tomi.ollila at iki.fi> writes:

>
> I got the same test results -- and could not figure out the reason through
> a brief look at the notmuch-new.c code.
>
> +1 for the series for now, hopefully we soon find out the resolution to the
> known broken tests.

OK, I pushed it, we'll see what happens. It'd be niced to sort this out
before the next release anyway.

d