[SPARK-1194] Fix the same-RDD rule for cache replacement

SPARK-1194: https://spark-project.atlassian.net/browse/SPARK-1194

In the current implementation, when selecting candidate blocks to be swapped out, once we find a block from the same RDD that the block to be stored belongs to, cache eviction fails  and aborts.

In this PR, we keep selecting blocks *not* from the RDD that the block to be stored belongs to until either enough free space can be ensured (cache eviction succeeds) or all such blocks are checked (cache eviction fails).