Fix flaky tests fails due inconsistent RNG usage

[asciimoth]

Summary

TestTrieRandom seeded a local RNG for generated addresses, but still used the package-global math/rand helpers for CIDR and peer selection. Under go test -race with repeated runs, that left the test only partially deterministic and made the slow reference router more likely to hit timeout-heavy paths which leads to test fails in like 1/100 runs.

This change switches the remaining random choices in device/allowedips_rand_test.go to the existing local seeded RNG so the test uses a single deterministic source.

Scope

• update TestTrieRandom to use rng.Intn(...) for CIDR and peer selection
• leave production code unchanged

Typos

I've also fixed some minor typos:

• HandshakeInitationRate -> HandshakeInitiationRate
• mis-parse -> miss-parse