server: stop logging TLS handshake errors in ErrorLog

ErrorLog is meant for panic logging only. It should only be used
for logging server implementation bugs, not for logging client
runtime errors.

conn.go

@@ -599,7 +599,6 @@ func (c *Conn) handleStartTLS() {
 	tlsConn := tls.Server(c.conn, c.server.TLSConfig)
 
 	if err := tlsConn.Handshake(); err != nil {
-		c.server.ErrorLog.Printf("TLS handshake error for %s: %v", c.conn.RemoteAddr(), err)
 		c.WriteResponse(550, EnhancedCode{5, 0, 0}, "Handshake error")
 		return
 	}

server.go

@@ -146,7 +146,6 @@ func (s *Server) handleConn(c *Conn) error {
 			c.conn.SetWriteDeadline(time.Now().Add(d))
 		}
 		if err := tlsConn.Handshake(); err != nil {
-			s.ErrorLog.Printf("TLS handshake error for %s: %v", tlsConn.RemoteAddr(), err)
 			return err
 		}
 	}