snap login tests are unreliable on ppc64el / powerpc

snap login tests are unreliable on ppc64el / powerpc: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). When building and running the cmd/snap test suite on ppc64el (and also powerpc), the tests covering snap login are flaky / fail outright. On amd64 they pass.