Destruction of a Ndb object did not always release the memory used
by Ndb<foo>Operations, and other similar objects, allocated by
NdbTranactions still being open when the owning Ndb object is destructed.

As all NdbTransactions are disconnected and the NdbTransaction objects freed
when the Ndb is destructed, all API objects belonging to these NdbTransactions
also becommes void.

This patch ensures that Ndb::doDisconnect() (Called by Ndb d'tor)
releases all API objects owned by its still remaing 'theTransactionList'

Furthermore, it also fixes an issue where a async prepared NdbTransaction
(NdbTransaction::theListState == InPreparedList) could be closed without
ever being executed. That caused NdbTransaction::release() to abort due
to this state not being expected.

Fixes some obvoius incorrect comments releated to code paths relevant for
this patch, and a likely merge problem where a copy of the decl of
 ::set- / ::getBuddyConPtr() had been pasted into another comment block.

Added a new test case to prove the leaks plugged by this patch.
Leaks will hit an assert in Ndb_free_list template when run
without patch.