[SPARK-12833][HOT-FIX] Reset the locale after we set it.

Author: Yin Huai <yhuai@databricks.com>

Closes #10778 from yhuai/resetLocale.

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/csv/CSVTypeCastSuite.scala

@@ -90,9 +90,14 @@ class CSVTypeCastSuite extends SparkFunSuite {
   }
 
   test("Float and Double Types are cast correctly with Locale") {
-    val locale : Locale = new Locale("fr", "FR")
-    Locale.setDefault(locale)
-    assert(CSVTypeCast.castTo("1,00", FloatType) == 1.0)
-    assert(CSVTypeCast.castTo("1,00", DoubleType) == 1.0)
+    val originalLocale = Locale.getDefault
+    try {
+      val locale : Locale = new Locale("fr", "FR")
+      Locale.setDefault(locale)
+      assert(CSVTypeCast.castTo("1,00", FloatType) == 1.0)
+      assert(CSVTypeCast.castTo("1,00", DoubleType) == 1.0)
+    } finally {
+      Locale.setDefault(originalLocale)
+    }
   }
 }