t9001, t9116: avoid pipes

t9001, t9116: avoid pipes

When grepping through the output of a command in the test suite, there
is always a chance that something goes wrong, in which case there would
not be anything useful to debug.

Let's redirect the output into a file instead, and grep that file, so
that the log can be inspected easily if the grep fails.

Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>