Fix memory leak in sudoku example (#607)

* Fix memory leak in sudoku example

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>

* right macro

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>

* remove iostream

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>

* remove hardcoded value

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>

* do one board copy instead of three copies

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>

* make task_group local

Signed-off-by: Mishin, Ilya <ilya.mishin@intel.com>