msg/simple/Pipe:the returned value for do_recv unequal to zero

msg/simple/Pipe:the returned value for do_recv unequal to zero

the returned value for do_recv unequal to zero:

ssize_t Pipe::do_recv(char *buf, size_t len, int flags)
{
again:
  ssize_t got = ::recv( sd, buf, len, flags );
  if (got < 0) {
    if (errno == EINTR) {
      goto again;
    }
    ldout(msgr->cct, 10) << **func** << " socket " << sd << " returned "
             << got << " " << cpp_strerror(errno) << dendl;
    return -1;
  }
  if (got == 0) {
    return -1;
  }
  return got;
}

so here '=' can be removed

Signed-off-by: zhang.zezhu <zhang.zezhu@zte.com.cn>