Fix #204, Check return value of calls to CFE_SB_Subscribe()

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to GSFC-SoftwareRelease@mail.nasa.gov and copied cfs-program@lists.nasa.gov.

Describe the contribution

• Fixes Calls to CFE_SB_Subscribe() are missing return checks #204
  • Checks the return from calls to CFE_SB_Subscribe() and saves it to the status variable.

Testing performed
GitHub CI actions all passing successfully.

Expected behavior changes
Failure of the calls to subscribe to the command and HK MIDs will set the status variable to an error state, and therefore halt further steps in the initialization.

System(s) tested on
Debian 12 using the current main branch of cFS bundle.

Contributor Info
Avi Weiss   @thnkslprpt