t3c will ensure config files are owned by ats

[jpappa200]

Closes: #6879

---

Which Traffic Control components are affected by this PR?

• Traffic Control Cache Config (t3c, formerly ORT)

What is the best way to verify this PR?

Build and install rpm, change file owner and group on some config files, queue updates on the cache, run t3c apply in syncds or badass, and verify owner and group have been set back to ats.

PR submission checklist

• This PR has tests
• This PR has documentation
• This PR has a CHANGELOG.md entry
• This PR DOES NOT FIX A SERIOUS SECURITY VULNERABILITY (see the Apache Software Foundation's security guidelines for details)

[ocket8888]

To test this I made a copy of t3c-diff's README, but it doesn't seem to detect that it doesn't have the right owner:

$ stat ./README.md 
  File: ./README.md
  Size: 3471      	Blocks: 8          IO Block: 4096   regular file
Device: 10303h/66307d	Inode: 17697181    Links: 1
Access: (0664/-rw-rw-r--)  Uid: ( 1000/ocket8888)   Gid: ( 1000/ocket8888)
Access: 2022-06-08 12:55:22.414520586 -0600
Modify: 2022-06-08 12:55:22.414520586 -0600
Change: 2022-06-08 12:55:22.414520586 -0600
 Birth: 2022-06-08 12:55:22.414520586 -0600
$ ./t3c-diff -l '<!--' -m 0664 -u 0 -g 0 -a ./README.md -b ./README.new.md
$ echo $?
0

[jpappa200]

the default value if left blank is 0
uid := getopt.IntLong("file-uid", 'u', 0, "User id the file being checked should have, default is running process's uid")
gid := getopt.IntLong("file-gid", 'g', 0, "Group id the file being checked should have, default is running process's gid")

if the value is 0 it will use the running process's uid/gid
if *uid == 0 { *uid = os.Geteuid() }
if *gid == 0 { *gid = os.Getgid() }
If you ran it as root it would find the difference. I could change the default value but it seemed logical to say that only the root user could say it should be owned by root.