Fix #392, seg fault - invalid file destination

[dmknutsen]

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
Fixes #392 - Adds logic to CF_CFDP_ResetTransaction to check if a transaction has previously been freed prior to resetting the transaction. This PR includes an additional requirement - which is now verified via an updated build verification test to ensure this condition is induced/verified as part of our build release. I also included an additional unit test to maintain 100% coverage.

Testing performed
Steps taken to test the contribution:

1. Unit/coverage testing
2. Build verification testing - which includes sending a PDUs with invalid destination filename(s) to ensure doing so is now being handled correctly.

System(s) tested on

• Ubuntu 20.04

Contributor Info - All information REQUIRED for consideration of pull request
Full name and company/organization/center of all contributors ("Personal" if individual work)
Dan Knutsen
NASA Goddard