Add timeout parameter and report request duration

[CoRfr]

Jenkins stopped responding to metrics while being functional for about 1 hour one night. It was busy at that time so I wonder if by extending the request timeout it would have been able to get some data, and if so I want to be able to monitor the request duration to see what it looks like.

Pull Request Checklist

Is this in reference to an existing issue?

General

• [x] Update Changelog following the conventions laid out on Our CHANGELOG Guidelines

• [ ] Update README with any necessary configuration snippets

• [ ] Binstubs are created if needed

• [x] RuboCop passes

• [x] Existing tests pass

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• [ ] Tests

• [ ] Add the plugin to the README

• [ ] Does it have a complete header as outlined here

Purpose

Known Compatibility Issues

[majormoses]

Thanks for your contribution to Sensu plugins! Without people like you submitting PRs we couldn't run the project. I will review it shortly.

[CoRfr]

For the testing artifacts:

$ bundle exec ./bin/metrics-jenkins.rb --scheme test --server 10.1.60.1 -p 8080 -t 10
...
test.timers.jenkins.node.carmd-nr-lxcid4bed9b5f162.builds.count 98 1510730423
test.timers.jenkins.node.carmd-nr-lxcid8d385e161f8.builds.count 14 1510730423
test.timers.jenkins.node.carmd-nr-lxcif4ce4684c67c.builds.count 79 1510730423
test.request.duration 41 1510730423

$ bundle exec ./bin/metrics-jenkins.rb --scheme test --server 10.1.60.1 -p 8080 --no-report-request-duration
...
test.timers.jenkins.node.carmd-nr-lxcid4bed9b5f162.builds.count 98 1510730443
test.timers.jenkins.node.carmd-nr-lxcid8d385e161f8.builds.count 14 1510730443
test.timers.jenkins.node.carmd-nr-lxcif4ce4684c67c.builds.count 79 1510730443

# On some AWS IP that doesn't exist
$ bundle exec ./bin/metrics-jenkins.rb --scheme test --server 10.101.1.5 -p 8080 -t 1
Jenkins Connection timed out
test.request.duration 1002 1510730920

$ bundle exec ./bin/metrics-jenkins.rb --scheme test --server 10.101.1.5 -p 8080 -t 1 2>/dev/null
test.request.duration 1002 1510730926

[majormoses]

released: https://rubygems.org/gems/sensu-plugins-jenkins/versions/1.4.0