MD `int32` return codes and variables should be converted to `CFE_Status_t`

Checklist

[x] I reviewed the Contributing Guide.
[x] I performed a cursory search to see if the bug report is relevant, not redundant, nor in conflict with other tickets.

Describe the bug MD has quite a few return codes (as well as local status/return variables which hold CFE return codes) that can be easily converted over to the CFE_Status_t typedef.

Expected behavior Use the more expressive CFE_Status_t and improve consistency with cFS.

Reporter Info Avi Weiss @thnkslprpt

nasa / MD

MD `int32` return codes and variables should be converted to `CFE_Status_t` #50