group: find_subpath method behavior is incorrect. it does not use path for new_group init

Hi! 
I have found that new_group method does not use parameter path.
If so, group will be created in top level.

suppose, that we want create subgroup.
parent/subgroup

if it happens in find_subpath with create all subpaths options, it will create subgroup directory with path equal to parent directory.

so, now, subgroup will have path as parent.