Add smoke test for sklearnex

[rosbo]

sklearnex was added in #1135

http:https://227237481

cc/ @napetrov

[rosbo]

Confirmed the test do use the Intel extensions for scikit-learn:

test_dbscan (test_sklearnex.TestSklearnex) ... Intel(R) Extension for Scikit-learn* enabled (https://github.com/intel/scikit-learn-intelex)

[napetrov]

@rosbo - thanks a lot, i thought that i've pushed tests as well.( Thanks for catching this!

[napetrov]

Suggested change

	from sklearn.cluster import DBSCAN
	class TestSklearnex(unittest.TestCase):
	def test_dbscan(self):
	from sklearnex import patch_sklearn
	patch_sklearn()
	class TestSklearnex(unittest.TestCase):
	def test_dbscan(self):
	from sklearnex.cluster import DBSCAN

I think that for package validation perspective - this would be the simplest way

There are 2 things related to patching:

1. You have to reimport "from sklearn.cluster import" after patching. Because patching process wouldn't affect already existing instances.
2. Patch would impact entire process - i'm not 100% sure how this would behave in case of the tests, but i'm afraid that it would have effect on following scikit calls, so unpatch would be required.

[rosbo]

Great suggestion. Applied. Thank you :)