Merge pull request #94 from aarondav/mesos-fix

Fix mesos urls

This was a bug I introduced in https://github.com/apache/incubator-spark/pull/71.
Previously, we explicitly removed the mesos:// part; with #71, this no longer occurs.

(cherry picked from commit 39d2e9b293768b6eeb291313ee94f3e02a0ad522)
Signed-off-by: Reynold Xin <rxin@apache.org>