Bug #25275 SINGLE USER MODE prevents ALTER on non-ndb tables for other mysqld nodes
- correction of part 1
    add ndb_waiter option to wait for single user mode


ndb/src/kernel/blocks/dbdict/Dbdict.cpp:
  Bug #25275 SINGLE USER MODE prevents ALTER on non-ndb tables for other mysqld nodes
  - correction of part 1
ndb/src/kernel/blocks/dbdict/Dbdict.hpp:
  Bug #25275 SINGLE USER MODE prevents ALTER on non-ndb tables for other mysqld nodes
  - correction of part 1
ndb/tools/waiter.cpp:
  add ndb_waiter option to wait for single user mode