Fix #63, clean up strncpy calls

[jphickey]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• 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
Call "strncpy" with the size parameter indicating the size of the destination buffer, rather than the input string length.

A buffer overflow was avoided due to a length check already in the code, but calling the function properly should avoid a warning.

Fixes #63

Testing performed
Build and run all tests
Send the FM_GET_DIR_FILE_CC and FM_GET_DIR_PKT_CC and confirm correct behavior.

Expected behavior changes
No compiler warnings.
No change to functionality.

System(s) tested on
Ubuntu 22.04

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

[jphickey]

Note - "Build and Run" workflow is now passing, log here: https://github.com/nasa/FM/actions/runs/3463996146

Other errors remain but those will be fixed by separate PRs.