Allow attaching TTYs to containers

[rgulewich]

This exposes a new passthrough parameter titusParameter.agent.ttyEnabled, which causes the container to be created with a tty (same as doing a docker run --tty).

[codecov]

Codecov Report

Merging #186 into master will increase coverage by 9.88%.
The diff coverage is 73.33%.

@@            Coverage Diff            @@
##           master    #186      +/-   ##
=========================================
+ Coverage   21.62%   31.5%   +9.88%     
=========================================
  Files          66      66              
  Lines        8393    8407      +14     
=========================================
+ Hits         1815    2649     +834     
+ Misses       6365    5437     -928     
- Partials      213     321     +108

Impacted Files	Coverage Δ
executor/mock/jobrunner.go	75.86% <100%> (+75.86%)	⬆️
executor/runtime/docker/docker.go	50.64% <50%> (+42.37%)	⬆️
executor/runtime/types/types.go	79.16% <75%> (+35.98%)	⬆️
filesystems/watcher.go	62% <0%> (+3.71%)	⬆️
config/config.go	97.1% <0%> (+4.34%)	⬆️
uploader/copy.go	50% <0%> (+5%)	⬆️
api/netflix/titus/agent.pb.go	22.35% <0%> (+5.63%)	⬆️
executor/runtime/docker/capabilities.go	88.88% <0%> (+11.11%)	⬆️
executor/runner/runner.go	60.62% <0%> (+11.87%)	⬆️
executor/runtime/container.go	91.3% <0%> (+13.04%)	⬆️
... and 10 more

[coveralls]

Pull Request Test Coverage Report for Build 2233

• 6 of 20 (30.0%) changed or added relevant lines in 3 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 22.851%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
executor/runtime/types/types.go	6	10	60.0%
executor/mock/jobrunner.go	0	5	0.0%
executor/runtime/docker/docker.go	0	5	0.0%

Totals
Change from base Build 2197:	0.02%
Covered Lines:	2456
Relevant Lines:	10748

---

💛 - Coveralls