[FIX] base: delete parent partner reset use_parent_address

When deleting a partner with some contacts, if the contacts had selected
the "use parent address" checkbox, the address of the contacts was stucked in
readonly mode (no checkbox to disable it).
Disable use_parent_address for orphan partners.

Fixes #3611 #3613
Merge branch '7.0' of https://github.com/odoo/odoo into 7.0-win32