Make sure all chunk involved in a merge have Bloom filters.  Fix a race where a chunk is merged and removed from the tree during creation of a Bloom filter.

refs #809
Have LSM compact logic match regular merges exactly: always create Bloom filters first.  If there are any concurrent reads in the tree, they will benefit from the Bloom filters, and this avoids having different paths through the merge code.
Switch || to && to fix build.
Merge pull request #887 from wiredtiger/merge-bloom-fix

Make sure all chunks involved in a merge have Bloom filters