[SPARK-20631][FOLLOW-UP] Fix incorrect tests.

## What changes were proposed in this pull request?

- Fix incorrect tests for `_check_thresholds`.
- Move test to `ParamTests`.

## How was this patch tested?

Unit tests.

Author: zero323 <[email protected]>

Closes #18085 from zero323/SPARK-20631-FOLLOW-UP.

(cherry picked from commit 1816eb3)
Signed-off-by: Yanbo Liang <[email protected]>

Author: zero323

python/pyspark/ml/tests.py

@@ -404,6 +404,18 @@ def test_copy_param_extras(self):
         self.assertEqual(tp._paramMap, copied_no_extra)
         self.assertEqual(tp._defaultParamMap, tp_copy._defaultParamMap)
 
+    def test_logistic_regression_check_thresholds(self):
+        self.assertIsInstance(
+            LogisticRegression(threshold=0.5, thresholds=[0.5, 0.5]),
+            LogisticRegression
+        )
+
+        self.assertRaisesRegexp(
+            ValueError,
+            "Logistic Regression getThreshold found inconsistent.*$",
+            LogisticRegression, threshold=0.42, thresholds=[0.5, 0.5]
+        )
+
 
 class EvaluatorTests(SparkSessionTestCase):
 
@@ -807,18 +819,6 @@ def test_logistic_regression(self):
         except OSError:
             pass
 
-    def logistic_regression_check_thresholds(self):
-        self.assertIsInstance(
-            LogisticRegression(threshold=0.5, thresholds=[0.5, 0.5]),
-            LogisticRegressionModel
-        )
-
-        self.assertRaisesRegexp(
-            ValueError,
-            "Logistic Regression getThreshold found inconsistent.*$",
-            LogisticRegression, threshold=0.42, thresholds=[0.5, 0.5]
-        )
-
     def _compare_params(self, m1, m2, param):
         """
         Compare 2 ML Params instances for the given param, and assert both have the same param value