Using the deprecated "space creation" request makes the UI create nested spaces

The deprecated tocreate=space&name=spaceName request should always result in creating a top level space (i.e. spaceName.WebHome), regardless of what existing document it is triggered from.

To reproduce:

1. create A.B.C.WebHome
2. use the URL /xwiki/bin/create/A/B/C/WebHome?name=spaceName&tocreate=space&template=
3. you should end up editing spaceName/WebHome and not /A/B/C/spaceName/WebHome