This allows basic master crash-safety
- Un-comment and update relevant parts of the code
- Make rocksdb_rpl suite work like other MyRocks testsuites
  (load the MyRocks plugin, don't start if it is not compiled in, etc)
- For now, disable all tests in the rocksdb_rpl suite.
- MariaDB-fication of rpl_rocksdb_2p_crash_recover test.