BUG#20823 testBackup FailMaster failing    few cases not handled properly (NF occurs).
BUG#20823 testBackup FailMaster failing
  
few cases not handled properly (NF occurs).


ndb/src/kernel/blocks/backup/Backup.cpp:
  Don't write fragment info if we haven't retreived any fragment info yet
  (FailMaster test 2)
      
  Go directly onto closing files if the tabPtr is RNIL (as we're in recovery)

flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,flynn1973/mariadb-aix,ollie314/server,ollie314/server,flynn1973/mariadb-aix,natsys/mariadb_10.2,davidl-zend/zenddbi,ollie314/server,ollie314/server,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,ollie314/server,davidl-zend/zenddbi,natsys/mariadb_10.2,natsys/mariadb_10.2,flynn1973/mariadb-aix,flynn1973/mariadb-aix,flynn1973/mariadb-aix,natsys/mariadb_10.2,natsys/mariadb_10.2,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2,flynn1973/mariadb-aix,ollie314/server,ollie314/server,ollie314/server,natsys/mariadb_10.2,davidl-zend/zenddbi,ollie314/server,slanterns/server,ollie314/server,ollie314/server,davidl-zend/zenddbi,davidl-zend/zenddbi,flynn1973/mariadb-aix,flynn1973/mariadb-aix,davidl-zend/zenddbi,davidl-zend/zenddbi,davidl-zend/zenddbi,natsys/mariadb_10.2