Cleanup sstables::mutation_reader::impl
Cleanup sstables::mutation_reader::impl

Pointer to sstable seems unnecessary.

Signed-off-by: Piotr Jastrzebski <2c0eb4a25a7cde333ff2d0860cb06051925fd74f@scylladb.com>
Message-Id: <a45e8853af2b5f896ec44144fbc26d3325a5ec0c.1479123740.git.2c0eb4a25a7cde333ff2d0860cb06051925fd74f@scylladb.com>

scylladb/scylla,raphaelsc/scylla,duarten/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,raphaelsc/scylla,scylladb/scylla,duarten/scylla,raphaelsc/scylla,scylladb/scylla