[SPARK-2041][SQL] Correctly analyze queries where columnName == tableName.

Author: Michael Armbrust <michael@databricks.com>

Closes #985 from marmbrus/tableName and squashes the following commits:

3caaa27 [Michael Armbrust] Correctly analyze queries where columnName == tableName.
Use pluggable clock in DAGSheduler #SPARK-2031

DAGScheduler supports pluggable clock like what TaskSetManager does.

Author: CrazyJvm <crazyjvm@gmail.com>

Closes #976 from CrazyJvm/clock and squashes the following commits:

6779a4c [CrazyJvm] Use pluggable clock in DAGSheduler