Fix #34 #37 #43 #44, UT cleanup, remove unreachable code, initialize FileMode on OS_stat failure

[skliper]

Checklist (Please check before submitting)

• I reviewed the Contributing Guide.
• I signed and emailed the appropriate Contributor License Agreement to [email protected] and copied [email protected].

Describe the contribution

• Fix fm_cmd_utils.c has branches that can't be reached (7/7) #34
• Fix Remove random numbers from unit tests #37
• Fix FM_ChildSizeTimeMode doesn't clear FileMode on OS_stat failure #43
• Fix Unreachable code in fm_child.c, EntryLength never larger than sizeof(DirListData.EntryName) #44

Testing performed
CI

Expected behavior changes
Will now initialize FileMode on OS_stat failure (won't write uninitialized data)

System(s) tested on
CI

Additional context
Can break up if needed, but easier to submit together since they resolve related coverage and UT issues.

Third party code
None

Contributor Info - All information REQUIRED for consideration of pull request
Jacob Hageman - NASA/GSFC