Always lock before calling setLatestMergedRevisionLocked (#131)
Always lock before calling setLatestMergedRevisionLocked (#131)

Also only call it after the head is properly set in
one case.

Put headLock-protected variables together.
keybase/client,keybase/client,keybase/kbfs,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client