CF writes to received SB buffer

[jphickey]

Checklist (Please check before submitting)

• 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
The output from CFE_SB_ReceiveBuffer() is a pointer to a shared buffer, and thus should be interpreted as const data. The only reason it is not qualified const in the API was due to backward compatibility concerns.

However, CF is actually writing to the buffer in two places.

To Reproduce
Send those commands

Expected behavior
Should not write to a buffer that was received from SB

Code snips

CF/fsw/src/cf_cmd.c

Lines 147 to 149 in a0d35e1

	/* make sure that the src and dst filenames are null terminated */
	tx->src_filename[sizeof(tx->src_filename) - 1] = 0;
	tx->dst_filename[sizeof(tx->dst_filename) - 1] = 0;

CF/fsw/src/cf_cmd.c

Lines 190 to 192 in a0d35e1

	/* make sure that the src and dst filenames are null terminated */
	tx->src_filename[sizeof(tx->src_filename) - 1] = 0;
	tx->dst_filename[sizeof(tx->dst_filename) - 1] = 0;

System observed on:
Inspection

Additional context
This is done to ensure null termination of the string. While a valid concern, a function like CFE_SB_MessageStringGet() should be used instead.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.