WL#1344: Test: Compare fragments function (test functionality)

The "compare fragements function" compares the data of one NDB
database node with another.  The function can be used for:
1. Debugging/Testing
2. Showing status to the user (what fragments exists, what fragments are 
   being recovered by the node recovery protocol)

The function can be implemented by a scan on one node and a pk 
lookup on the other.

(The functionality was suggested during the MySQL Cluster tutorial in
Bordeaux.)