Test ndb.ndb_read_local was extended to be able to test that read backup was
used when accessing fully replicated blob tables.

It does not in all cases, and test extensions also demonstrates other bugs.

Changes made:

1) It adds testing for two and three node groups for fully replicated tables.

2) Move testing of read backup on top, since it makes only sence for one node
  group, otherwise not all data is available locally.

3) Adding test to check that one can turn on READ_BACKUP online.  Related to
Bug#24424459 READBACKUP PROPERTY NOT PROPAGATED TO UI AND BLOB TABLES IN ALTER TABLE

4) Adding a table 'hints' that are used to hint a transaction agains different
  nodes.

5) Make all transactions hinted using 'hints' table, loop all tests with hint
  to different nodes.

6) Using the 'hints' table for make all transactions hinted also avoids
  otherwise unhinted transactions, as scans, to never use a dbtc on a node
  without data, such as node group less nodes.

7) Check replica count also for unique index and blob table.

8) Check number of nodes with data for table, unique index, and, blob table.

9) Add flags to avoid parts of test due to bugs, these should be removed than
  corresponding bugs are fixed.

10) Change check for debug build, to check for error insert support.