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

Checklist

[x] I reviewed the Contributing Guide.
[x] 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 #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

nasa / to_lab

Fix #204, Check return value of calls to `CFE_SB_Subscribe()` #205