Revert "Scripts: check PLUGIN_ROCKSDB to skip cloning it"
Revert "Scripts: check PLUGIN_ROCKSDB to skip cloning it"

This reverts commit a86d6bad549009d8817baf3388bc371c66e98b00.

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2