Fix folder name encoding in em_folder_utils_create_folder().

When creating a top-level folder, the folder name was still URI-encoded.
So for example "Top Level Folder" was coming out "Top%20Level%20Folder".

The em_folder_tree_store_root_selected() "if" branch is uncommented and
looks unnecessary to me, so I'm removing it.  Always parse the URI with
e_mail_folder_uri_parse(), which produces a decoded folder name.