t3c remove stale git lock file

[jpappa200]

When using git to track changes in etc/trafficserver sometimes the lock file isn't cleared and git will stop updating. This PR will cause t3c-apply to look for a lock file that is more than 5 min old and remove if it exists.

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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?

The best way to verify and to create an index.lock file in /opt/trafficserver/etc/trafficserver/.git/ and tail reval.log and syncds.log when the file is 5 minutes old it will be cleared.

If this is a bugfix, which Traffic Control versions contained the bug?

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)

[codecov]

Codecov Report

Merging #7346 (3afd237) into master (3aca837) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@             Coverage Diff              @@
##             master    #7346      +/-   ##
============================================
- Coverage     25.07%   25.06%   -0.01%     
  Complexity       98       98              
============================================
  Files           593      593              
  Lines         73616    73644      +28     
  Branches         90       90              
============================================
+ Hits          18459    18460       +1     
- Misses        53406    53433      +27     
  Partials       1751     1751              

Flag	Coverage Δ
golib_unit	53.16% <ø> (+<0.01%)	⬆️
grove_unit	4.60% <ø> (ø)
t3c_unit	5.33% <0.00%> (-0.03%)	⬇️
traffic_monitor_unit	20.43% <ø> (ø)
traffic_ops_unit	19.70% <ø> (ø)
traffic_stats_unit	10.41% <ø> (ø)
unit_tests	22.59% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cache-config/t3c-apply/t3c-apply.go	0.00% <0.00%> (ø)
cache-config/t3c-apply/util/gitutil.go	0.00% <0.00%> (ø)
lib/go-atscfg/serverunknown.go	79.66% <0.00%> (+1.69%)	⬆️

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[traeak]

These look good to me.