Fix #7, consolidate functions for managing tables

[havencarlson]

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
Fix #7, consolidate SC_ManageAtsTable(), SC_ManageRtsTable(), and SC_ManageAppendTable()

Testing performed
Unit testing

Expected behavior changes
no impact to behavior

System(s) tested on

• OS: Ubuntu 18.04

Contributor Info - All information REQUIRED for consideration of pull request
Haven Carlson - NASA

[github-advanced-security]

Found 18 potential problems in the proposed changes. Check the Files changed tab for more details.

[skliper]

Looks fine to me from a quick skim. Recommend adding someone from the core cFS team to review in detail. Could some of the related coverage tests be simplified based on the consolidation (no need to cover shared code 3 different times)? Good to show it still passes the original tests though! Maybe simplify UT's as a follow on issue (if it can actually be simplified)?