[SPARK-4169] [Core] Accommodate non-English Locales in unit tests

For me the core tests failed because there are two locale dependent parts in the code.
Look at the Jira ticket for details.

Why is it necessary to check the exception message in isBindCollision in
https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/util/Utils.scala#L1686
?

Author: Niklas Wilcke <1wilcke@informatik.uni-hamburg.de>

Closes #3036 from numbnut/core-test-fix and squashes the following commits:

1fb0d04 [Niklas Wilcke] Fixing locale dependend code and tests