MB-36976 Change magma_enable_block_cache default to true
MB-36976 Change magma_enable_block_cache default to true

Block cache is now stable so turn on block cache by default.

Change-Id: I5160f0699fefeb9c54b25b60ea24b661cd87d98f
Reviewed-on: http://review.couchbase.org/118151
Tested-by: Build Bot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@couchbase.com>

daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine