MariaRocks port

- Use rocksdb_sys_vars/my.cnf so that one can run tests from that suite
  by just  "./mtr rocksdb_sys_vars.$TESTNAME"
- Add rocksdb and rocksdb_sys_vars to the set of default test suites.
  Don't run with embedded server, yet.

storage/rocksdb/mysql-test/rocksdb/suite.pm

+package My::Suite::Rocksdb_sys_vars;
+
+@ISA = qw(My::Suite);
+
+sub is_default { not $::opt_embedded_server }
+
+bless { };
+

storage/rocksdb/mysql-test/rocksdb_sys_vars/my.cnf

+!include include/default_my.cnf
+
+[server]
+rocksdb
+skip-innodb
+default-storage-engine=rocksdb
+
+
+sql-mode=NO_ENGINE_SUBSTITUTION
+explicit-defaults-for-timestamp=1
+rocksdb_lock_wait_timeout=1
+rocksdb_strict_collation_check=0

storage/rocksdb/mysql-test/rocksdb_sys_vars/suite.pm

+package My::Suite::Rocksdb_sys_vars;
+
+@ISA = qw(My::Suite);
+
+sub is_default { not $::opt_embedded_server }
+
+bless { };
+