message: Fix interminnent pgsql plugin testing issue
diff: @@ -1100,7 +1100,7 @@ mod tests {
  assert_eq!(err, ErrorCode::Success);
  // update metadata to some new metadata
  - let metadata2 = _metadata2();
  + let metadata2 = _metadata2_cstring();
  let err = PostgresWallet::set_storage_metadata(handle, metadata2.as_ptr());
  assert_eq!(err, ErrorCode::Success);
  @@ -1811,7 +1811,7 @@ mod tests {
  CString::new(foo).unwrap()
  }
  - fn _metadata2() -> Vec<i8> {
  + fn _metadata2() -> Vec<u8> {
  return vec![
  2, 3, 4, 5, 6, 7, 8, 9,
  2, 3, 4, 5, 6, 7, 8, 9,
  @@ -1824,6 +1824,11 @@ mod tests {
  ];
  }
  + fn _metadata2_cstring() -> CString {
  + let foo = _metadata2();
  + CString::new(foo).unwrap()
  + }
  +
  fn _type(i: u8) -> CString {
  let type_ = vec![i, 1 + i, 2 + i];
  CString::new(type_.clone()).unwrap()
  