fix(kubernetes): Coordinate Runtime's RunContainer/TailContainer via a channel

[cognifloyd]

The Kubernetes runtime needs to start streaming logs before the container starts.
The Docker runtime needs to start the container before streaming longs.
With both running in goroutines, the Runtime can block one method until the other completes in whichever order makes sense for that Runtime.

Alternate to #277

[codecov]

Codecov Report

Merging #286 (a6417a6) into master (c1d4563) will decrease coverage by 0.77%.
The diff coverage is 97.01%.

❗ Current head a6417a6 differs from pull request most recent head b91cf19. Consider uploading reports for the commit b91cf19 to get more accurate results

@@            Coverage Diff             @@
##           master     #286      +/-   ##
==========================================
- Coverage   78.91%   78.13%   -0.78%     
==========================================
  Files          67       67              
  Lines        4870     4954      +84     
==========================================
+ Hits         3843     3871      +28     
- Misses        884      944      +60     
+ Partials      143      139       -4     

Impacted Files	Coverage Δ
runtime/kubernetes/container.go	55.92% <42.85%> (-21.69%)	⬇️
executor/linux/secret.go	73.62% <100.00%> (+3.15%)	⬆️
executor/linux/service.go	64.14% <100.00%> (+1.60%)	⬆️
executor/linux/step.go	66.38% <100.00%> (+1.27%)	⬆️
executor/local/service.go	92.17% <100.00%> (+1.35%)	⬆️
executor/local/step.go	88.65% <100.00%> (+1.55%)	⬆️
runtime/docker/container.go	85.18% <100.00%> (+0.31%)	⬆️
... and 1 more

[cognifloyd]

Closing in favor of #303