raftstore: fix redundant heartbeat (#3864)
raftstore: fix redundant heartbeat (#3864)

* fix the heartbeat

Signed-off-by: rleungx <98ca95cd24c810cea97a0e53f67d648652b7b2cf@gmail.com>
pingcap/tikv,BusyJay/tikv,BusyJay/tikv,c4pt0r/tikv,BusyJay/tikv,pingcap/tikv,BusyJay/tikv