Remaining int32 CFE status variables should be converted to `CFE_Status_t`

[thnkslprpt]

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 sample_app has a few remaining int32 variables and return codes that can be 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