When unsharing from self in a group share situation, the share items
passed to the post_unshareFromSelf hook were using the wrong format in
which the attribute names (ex: "share_type") have non camel-case format.

This fix makes sure that in group sharing case we use the correct
format. It looks like the code was already producing it but in
array_merge it was not using it and adding the unprocessed one.