[IMPROVED] Also reset clseq to avoid possible immediate sequence mismatch (#4366)

Signed-off-by: Derek Collison <derek@nats.io>

server/stream.go

@@ -842,7 +842,7 @@ func (mset *stream) clearCLFS() uint64 {
 	mset.mu.Lock()
 	defer mset.mu.Unlock()
 	clfs := mset.clfs
-	mset.clfs = 0
+	mset.clfs, mset.clseq = 0, 0
 	return clfs
 }