remove currentStateLock

[darioush]

Why this should be merged

This lock is not present in upstream and we hold pool.mu in all cases this lock is held so it's not providing any additional guarantees.

How this works

Removes code

How this was tested

CI

Need to be documented?

N/A

Need to update RELEASES.md?

N/A

[qdm12]

Maybe that's totally paranoid, but given the Init method on the LegacyPool does assign currentState, shall we add pool.mu.Lock() and unlock in that function, just in case ™️ Or not, if it's a copy pasta from geth 🤷