Fixing a bug with handling unexpected exceptions in Controller

[DanSimon]

This fixes a bug uncovered by another bug that will be in a separate PR against master. Basically when ServiceClient threw an exception, it got caught by InputController as an unexpected error resulting in killing the connection (which it should do). The problem was that it was calling disconnect instead of kill, which meant ServiceClient would not handle the disconnect as an error and would not try to reconnect.

The solution was a little more involved because in the case of server connections, calling disconnect() is actually what we want to do, because when pipelining responses we want the server connection to be able to send back any responses for successfully processed requests before closing the connection.

So the solution is to basically punt the decision of which function to call to the downstream handler, aka ServiceServer or ServiceClient. So now the onFatalError event handler method is required to return a FatalErrorAction which instructs the controller how to behave.

[codecov-io]

Codecov Report

Merging #517 into develop will decrease coverage by 0.04%. The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           develop    #517      +/-   ##
==========================================
- Coverage    84.74%   84.7%   -0.05%     
==========================================
  Files           98      98              
  Lines         4288    4289       +1     
  Branches       348     342       -6     
==========================================
- Hits          3634    3633       -1     
- Misses         654     656       +2

Impacted Files	Coverage Δ
...in/scala/colossus/streaming/StreamTranscoder.scala	84.21% <ø> (ø)	:arrow_up:
...ossus/protocols/http/streaming/StreamService.scala	82.35% <0%> (-10.99%)	:arrow_down:
...scala/colossus/protocols/websocket/Websocket.scala	91.07% <0%> (-0.83%)	:arrow_down:
...rc/main/scala/colossus/service/ServiceClient.scala	94.81% <100%> (-0.04%)	:arrow_down:
...rc/main/scala/colossus/controller/Controller.scala	83.33% <100%> (+8.33%)	:arrow_up:
...rc/main/scala/colossus/service/ServiceServer.scala	92.78% <100%> (-0.08%)	:arrow_down:

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[benblack86]

👍

Should we wait for the mapTry fix before merging and cutting RC4?

[DanSimon]

This can be merged now, but we should wait for the mapTry fix to do the release. That one should be much more straight-forward so I should have a PR ready soon.