breaks auto increment

The auto_increment value was not initialized if
the first statement after opening a table was
an 'UPDATE'.

solution was to check initialize if it was not,
before trying to increase it in update.

mysql-test/suite/parts/inc/partition_auto_increment.inc:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Added tests for verifying the bug and show some more
  auto_increment flaws
mysql-test/suite/parts/r/partition_auto_increment_archive.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
mysql-test/suite/parts/r/partition_auto_increment_blackhole.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
mysql-test/suite/parts/r/partition_auto_increment_innodb.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
mysql-test/suite/parts/r/partition_auto_increment_memory.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
mysql-test/suite/parts/r/partition_auto_increment_myisam.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
mysql-test/suite/parts/r/partition_auto_increment_ndb.result:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Updated test results, due to added tests
sql/ha_partition.cc:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  make sure that the auto_increment value is initialized
  before updating it.
  
  (missed initializing in mysql_update_row).
sql/ha_partition.h:
  Bug#40176: update as first partitioning statement
  breaks auto increment
  
  Assert that it is initialized, before updating
  the auto_increment value