Fix data race in newWatchEventPeer

[dawn-minion]

This method was attempting to read from peer.fsm before acquiring a read lock, leading to a data race as this struct is written by a different goroutine in parallel. Commit moves the call to RLock before the first read from the struct.

Issue was flagged when the project was built with Golang's data race detector.

[fujita]

How this is related with?
#2715

We need both or either?

[dawn-minion]

All 3 are separate data races, and all 3 are needed - I opened them as 3 pull requests in case changes were needed.

EDIT: I can merge it in to one of course if you prefer.

[fujita]

thanks