Replace msg module use of CFE_MISSION_SPACECRAFT_ID with CFE_PSP_GetSpacecraftId()

**Is your feature request related to a problem? Please describe.**
CFE_MISSION_SPACECRAFT_ID is pending deprecation, see #827

**Describe the solution you'd like**
Replace with CFE_PSP_GetSpacecraftId()

**Describe alternatives you've considered**
None

**Additional context**
None

**Requester Info**
Jacob Hageman - NASA/GSFC