Incomplete OSAL error conversion in CFE_ES_ReloadApp

[nmullane]

Describe the bug
The CFE_ES_ReloadApp function uses the function OS_stat to perform its work. The error handling in CFE_ES_ReloadApp assumes any failure in OS_stat is due to a file IO issue. This may not be the case because if a null pointer is passed in as the file name OS_stat will return an OS_INVALID_POINTER, but this specific error code will be ignored and CFE_ES_ReloadApp will just output CFE_ES_FILE_IO_ERR instead of a CFE_ES_BAD_ARGUMENT.

To Reproduce
Steps to reproduce the behavior:

1. Call CFE_ES_ReloadApp with a null pointer for filename. It will return a CFE_ES_FILE_IO_ERR when the real issue was a bad argument.

Expected behavior
CFE_ES_ReloadApp could include a null check itself to provide a more specific error message or the OS_INVALID_POINTER returned by OS_stat could be converted to a specific CFE error code.

Additional context
See #1672 for a similar error conversion issue

Reporter Info
Niall Mullane - GSFC 582 Intern