chore(discovery): adjust error message
Merge pull request #706 from unihorn/62

bump(goraft/raft): cfa43a115
Merge pull request #694 from unihorn/59

chore(discovery): adjust error message
fix(peer_server): recover from outage with discovery

This patch also contains the refactor of find cluster process.
It is changed based on @xiangli-cmu 's commits in 627 issue.