tests: allow 2 MiB RSS
tests: allow 2 MiB RSS

On some systems we use more than 1 MiB RSS
(because of glibc?). Allow that.

Fixes https://github.com/rfjakob/earlyoom/issues/221

rfjakob/earlyoom,rfjakob/earlyoom,rfjakob/earlyoom,rfjakob/earlyoom