"4b9a34a85425d1279b471b2ff0b0f2462328929c "Merge sstable_data_source
into sstable_mutation_reader" has introduced unintentional changes, some
of them causing excessive read amplification during empty range reads.
The following patches restore the previous behaviour."
* tag 'fix-read-amplification/v1' of https://github.com/pdziepak/scylla:
sstables: set _read_enabled to false if possible
sstables: set _single_partition_read for single parititon reads
(cherry picked from commit 772d1f47d7)