Recommend using FcnCode (instead of CommandCode) terminology in the code

[thnkslprpt]

Checklist

• I reviewed the Contributing Guide.
• I performed a cursory search to see if the bug report is relevant, not redundant, nor in conflict with other tickets.

Describe the bug
Copy of nasa/sample_app#167

Expected behavior
Rename the CommandCode variable in CI_LAB_ProcessGroundCommand() to FcnCode to better align with the cFE API.

Code snips

ci_lab/fsw/src/ci_lab_app.c

Lines 225 to 232 in a5e8b4b

	void CI_LAB_ProcessGroundCommand(CFE_SB_Buffer_t *SBBufPtr)
	{
	CFE_MSG_FcnCode_t CommandCode = 0;
	CFE_MSG_GetFcnCode(&SBBufPtr->Msg, &CommandCode);
	/* Process "known" CI task ground commands */
	switch (CommandCode)

Reporter Info
Avi Weiss @thnkslprpt