Fix #2536, msg api test buffer overrun

[jphickey]

Checklist (Please check before submitting)

• [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 Corrects the buffer type used in the msg api tests, to be sized appropriately for either command or telemetry. When the secondary header accessor from the other type is used, it will not overrun the buffer.

Fixes #2536

Testing performed Run functional tests

Expected behavior changes No buffer overrun reports when using -fsanitize=address

System(s) tested on Debian

Contributor Info - All information REQUIRED for consideration of pull request Joseph Hickey, Vantage Systems, Inc.

[jphickey]

Should be ready now. This now has two separate buffers (cmd and tlm) and allows either operation (checksum, timestamp) to independently work or not work on either buffer.