EC2 Enhancements

[ansoncfit]

• Refactor to reduce EC2-specific code in Broker
• Launch method for both on-demand and spot instances (step toward Boost regional analyses #192)

Questions

• Refactor overloaded createWorkersInCategory?
• What should be synchronized (note FIXME in BrokerController)
• Is the try/catch block in BrokerController unnecessary?
• Should we just automatically add spot workers after the first few regional tasks are complete?

[codecov-io]

Codecov Report

Merging #201 into dev will decrease coverage by 0.61%.
The diff coverage is 3.3%.

@@             Coverage Diff              @@
##                dev     #201      +/-   ##
============================================
- Coverage     24.35%   23.73%   -0.62%     
  Complexity      103      103              
============================================
  Files            59       61       +2     
  Lines          2275     2330      +55     
  Branches        206      211       +5     
============================================
- Hits            554      553       -1     
- Misses         1687     1745      +58     
+ Partials         34       32       -2

Impacted Files	Coverage Δ	Complexity Δ
...m/conveyal/taui/analysis/broker/WorkerCatalog.java	25% <0%> (-0.65%)	2 <0> (ø)
...com/conveyal/taui/analysis/broker/EC2Launcher.java	0% <0%> (ø)	0 <0> (?)
.../taui/analysis/broker/EC2RequestConfiguration.java	0% <0%> (ø)	0 <0> (?)
...in/java/com/conveyal/taui/analysis/broker/Job.java	0% <0%> (ø)	0 <0> (ø)	⬇️
...om/conveyal/taui/controllers/BrokerController.java	21.78% <0%> (ø)	6 <0> (ø)	⬇️
...java/com/conveyal/taui/analysis/broker/Broker.java	15.32% <14.28%> (+2.82%)	4 <0> (ø)	⬇️

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[ansoncfit]

@abyrd This should be ready for review. Our decisions on the questions above have been incorporated, and testing on staging has gone well.

Also, I wonder if using the synchronizedMap will resolve #172

[ansoncfit]

To answer the last question: yes, these changes now include having the broker automatically start spot instances after receiving a few regional tasks. Note TARGET_TASKS_PER_WORKER and AUTO_START_SPOT_INSTANCES_AT_TASK.