message: Use BP3 for now in Write Mode when user sets BPFile
diff: @@ -435,8 +435,9 @@ Engine &IO::Open(const std::string &name, const Mode mode,
  /* BPFile for read needs to use BP4 or BP3 depending on the file's version
  */
  - if ((engineTypeLC == "bpfile" || engineTypeLC == "bp") &&
  - mode == Mode::Read)
  + if ((engineTypeLC == "bpfile" || engineTypeLC == "bp"))
  + {
  + if (mode == Mode::Read)
  {
  if (adios2sys::SystemTools::FileIsDirectory(name))
  {
  @@ -447,6 +448,11 @@ Engine &IO::Open(const std::string &name, const Mode mode,
  engineTypeLC = "bp3";
  }
  }
  + else
  + {
  + engineTypeLC = "bp3";
  + }
  + }
  if (isDefaultEngine || engineTypeLC == "bp3")
  {
  