message: refactor(http1): apply a few clippy suggestions
  use is_empty() instead of .len()
  use if let instead of match
diff: @@ -65,7 +65,7 @@ impl Http1Transaction for Server {
  const LOG: &'static str = "{role=server}";
  fn parse(buf: &mut BytesMut, ctx: ParseContext) -> ParseResult<RequestLine> {
  - if buf.len() == 0 {
  + if buf.is_empty() {
  return Ok(None);
  }
  @@ -575,7 +575,7 @@ impl Http1Transaction for Client {
  fn parse(buf: &mut BytesMut, ctx: ParseContext) -> ParseResult<StatusCode> {
  // Loop to skip information status code headers (100 Continue, etc).
  loop {
  - if buf.len() == 0 {
  + if buf.is_empty() {
  return Ok(None);
  }
  // Unsafe: see comment in Server Http1Transaction, above.
  @@ -615,8 +615,7 @@ impl Http1Transaction for Client {
  let name = header_name!(&slice[header.name.0..header.name.1]);
  let value = header_value!(slice.slice(header.value.0, header.value.1));
  - match name {
  - header::CONNECTION => {
  + if let header::CONNECTION = name {
  // keep_alive was previously set to default for Version
  if keep_alive {
  // HTTP/1.1
  @@ -626,8 +625,6 @@ impl Http1Transaction for Client {
  // HTTP/1.0
  keep_alive = headers::connection_keep_alive(&value);
  }
  - },
  - _ => (),
  }
  headers.append(name, value);
  }
  @@ -734,12 +731,9 @@ impl Client {
  Some(Method::HEAD) => {
  return Ok(Some((DecodedLength::ZERO, false)));
  }
  - Some(Method::CONNECT) => match inc.subject.as_u16() {
  - 200...299 => {
  + Some(Method::CONNECT) => if let 200...299 = inc.subject.as_u16() {
  return Ok(Some((DecodedLength::ZERO, true)));
  - },
  - _ => {},
  - },
  + }
  Some(_) => {},
  None => {
  trace!("Client::decoder is missing the Method");
  