Fix for empty explainers

[adriangonz]

Fixes #1593

Changelog

• Fix typo on basicAmbassadorTest function.
• Add helper isEmptyExplainer().
• Use helper to check if we should create an explainer deployment and/or add an explainer label.
• Migrate operator/controller/labels_test.go to Gomega. Apparently they weren't running with t.Run().
• Add empty explainer tests for controllers.createExplainer().

[adriangonz]

/cc @cliveseldon @glindsell @axsaucedo

[adriangonz]

/test integration

[seldondev]

Wed Mar 25 16:15:58 UTC 2020
The logs for [pr-build] [1] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-1604/1.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-1604 --build=1

[seldondev]

Wed Mar 25 16:16:37 UTC 2020
The logs for [integration] [3] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-1604/3.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-1604 --build=3

[seldondev]

Wed Mar 25 16:17:12 UTC 2020
The logs for [lint] [2] will show after the pipeline context has finished.
https://github.com/SeldonIO/seldon-core/blob/gh-pages/jenkins-x/logs/SeldonIO/seldon-core/PR-1604/2.log

impatient try
jx get build logs SeldonIO/seldon-core/PR-1604 --build=2

[ukclivecox]

/lgtm

[seldondev]

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[ukclivecox]

I assume integration tests will fail for prepackaged server until that PR is merged?

[adriangonz]

That is a good point @cliveseldon. Only those should fail.

[seldondev]

@adriangonz: The following test failed, say /retest to rerun them all:

Test name	Commit	Details	Rerun command
integration	ca51117	link	/test integration

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[adriangonz]

Those were the only ones failing. Should we merge then @cliveseldon?