Support for specifying additional arguments to concord tasks

[justinabrahms]

This provides a mechanism to pass additional arguments to concord. Concord API docs which show how to do this are here: https://concord.walmartlabs.com/docs/api/process.html#form-data

I added some additional tests for the concord work, which didn't appear to have any. When running make test, there was an error (before I made any changes) because go fmt seems to disagree with goimports on the order of things. I updated goimports to no avail.

I'm not certain how to test this with concord. Do y'all have a test harness for that?

[codecov-commenter]

Codecov Report

Merging #607 into master will increase coverage by 0.63%.
The diff coverage is 93.75%.

@@            Coverage Diff             @@
##           master     #607      +/-   ##
==========================================
+ Coverage   55.00%   55.64%   +0.63%     
==========================================
  Files          62       62              
  Lines        5303     5314      +11     
==========================================
+ Hits         2917     2957      +40     
+ Misses       1959     1920      -39     
- Partials      427      437      +10     

Impacted Files	Coverage Δ
pkg/loadtester/concord.go	29.41% <93.75%> (+29.41%)	⬆️

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[stefanprodan]

When running make test, there was an error

Make sure you're using go 1.14, the fmt changed from 1.13 to 1.14

[justinabrahms]

@stefanprodan I'm happy to make that change. Can you update the docs here that the go version is 1.14, not 1.13? https://docs.flagger.app/dev/dev-guide#setup-dev-environment I looked for the repo on github, but couldn't find it, else I'd submit a PR for it.

[stefanprodan]

@justinabrahms the dev docs are here https://github.com/weaveworks/flagger/blob/master/docs/gitbook/dev/dev-guide.md

[justinabrahms]

#608 for that other change.

[stefanprodan]

@tebo-ernstberger can you please review this PR? I'm not familiar with concord

[justinabrahms]

cc @ta924

[stefanprodan]

LGTM

Thanks @justinabrahms