storage_proxy: devirtualize total_block_for()
storage_proxy: devirtualize total_block_for()

total_block_for() is defined only in base class, so make it non virtual.

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