and the original engine is disabled

Missing check that engine is available.

mysql-test/include/not_blackhole.inc:
  new include file
mysql-test/r/partition_not_blackhole.result:
  new result file
mysql-test/std_data/parts/t1_blackhole.frm:
  blackhole partitioned table .frm file:
  create table `t1` (`id` int primary key) engine=blackhole
  partition by key () partitions 1;
mysql-test/std_data/parts/t1_blackhole.par:
  .par file matching blackhole partitioned .frm
mysql-test/t/partition_not_blackhole-master.opt:
  new master-opt to disable blackhole if compiled in.
mysql-test/t/partition_not_blackhole.test:
  New test
sql/ha_partition.cc:
  Added check that engine is available.