References to previous cell in read path should be avoided

Came as part of review discussion in HBASE-15554. If there are references kept to previous cells in the read path, with the Ref count based eviction mechanism in trunk, then chances are there to evict a block backing the previous cell but the read path still does some operations on that garbage collected previous cell leading to incorrect results.
Areas to target
-> Storescanner
-> Bloom filters (particularly in compaction path)
Thanks to Anoop Sam John to point out this in bloomfilter path. But we found it could be in other areas also.