When `--packages` is specified with spark-shell the classes from those packages cannot be found, which I think is due to some of the changes in SPARK-12343.

Tested manually with both scala 2.10 and 2.11 repls.

vanzin davies can you guys please review?

Author: Marcelo Vanzin <vanzin@cloudera.com>
Author: Nezih Yigitbasi <nyigitbasi@netflix.com>

Closes #13709 from nezihyigitbasi/SPARK-15782.