worker: Overrule resource hog runner container on startup

[victorges]

What does this pull request do? Explain your changes. (required)
This is to make sure that ai-runner containers that have gone rogue and are consuming
all of the system resources (normally VRAM) are able to get killed by a restarting O.

The problem used to be that the O died out of VRAM when starting and couldnt' get to kill
the runner. This change makes sure that we do it ASAP in the startup so that it frees resources
so the new O can start.

Specific updates (required)

• Remove existing containers ASAP in worker startup

How did you test each of these updates (required)
Not yet.

Does this pull request close any open issues?
Fixes INF-350

Checklist:

• Read the contribution guide
• make runs successfully
• All tests in ./test.sh pass
• README and other documentation updated
• Pending changelog updated

[linear]

INF-350 CUDA memory errors preventing O to restart

[codecov]

Codecov Report

❌ Patch coverage is 12.12121% with 29 lines in your changes missing coverage. Please review.
✅ Project coverage is 31.93740%. Comparing base (d8e520a) to head (41205d5).
⚠️ Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
ai/worker/docker.go	19.04762%	14 Missing and 3 partials ⚠️
cmd/livepeer/starter/starter.go	0.00000%	11 Missing ⚠️
ai/worker/worker.go	0.00000%	1 Missing ⚠️

Additional details and impacted files

@@                 Coverage Diff                 @@
##              master       #3749         +/-   ##
===================================================
- Coverage   31.94444%   31.93740%   -0.00704%     
===================================================
  Files            158         158                 
  Lines          47520       47543         +23     
===================================================
+ Hits           15180       15184          +4     
- Misses         31437       31455         +18     
- Partials         903         904          +1     

Files with missing lines	Coverage Δ
ai/worker/worker.go	0.00000% <0.00000%> (ø)
cmd/livepeer/starter/starter.go	6.88863% <0.00000%> (-0.04378%)	⬇️
ai/worker/docker.go	69.15078% <19.04762%> (-1.61571%)	⬇️

... and 2 files with indirect coverage changes

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Files with missing lines	Coverage Δ
ai/worker/worker.go	0.00000% <0.00000%> (ø)
cmd/livepeer/starter/starter.go	6.88863% <0.00000%> (-0.04378%)	⬇️
ai/worker/docker.go	69.15078% <19.04762%> (-1.61571%)	⬇️

... and 2 files with indirect coverage changes

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