Pin dependencies and update vendors

vendor/github.com/soheilhy/cmux/cmux.go

@@ -116,8 +116,9 @@ type cMux struct {
 func matchersToMatchWriters(matchers []Matcher) []MatchWriter {
 	mws := make([]MatchWriter, 0, len(matchers))
 	for _, m := range matchers {
+		cm := m
 		mws = append(mws, func(w io.Writer, r io.Reader) bool {
-			return m(r)
+			return cm(r)
 		})
 	}
 	return mws

vendor/github.com/soheilhy/cmux/matchers.go

@@ -240,6 +240,11 @@ func matchHTTP2Field(w io.Writer, r io.Reader, name string, matches func(string)
 
 		switch f := f.(type) {
 		case *http2.SettingsFrame:
+			// Sender acknoweldged the SETTINGS frame. No need to write
+			// SETTINGS again.
+			if f.IsAck() {
+				break
+			}
 			if err := framer.WriteSettings(); err != nil {
 				return false
 			}