test: increase cffi timeout

By default, the test suite uses 2min for other tests and 5s for cffi
tests. Sporadically, this leads to test failures caused by the timeout
on slower or loaded test infrastructure (as seen on ppc64le in Fedora's
infrastructure during branch time).

Increase the cffi timeout to the same 2m=120s.

Signed-off-by: Michael J Gruber <git@grubix.eu>