raft: fsm: don't advance commit index further than match_idx during read_quorum
raft: fsm: don't advance commit index further than match_idx during read_quorum

It's not safe to advance the commit index further than match_idx since
beyond that point the follower's log may be outdated.

Fixes #10578.

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla