Fix permanent delete of several documents

When deleting several documents permanently (e.g. from the trash tab) using the "select all" checkbox, sometimes only one of the documents is really deleted (cannot be reproduced every time).
Performing the operation again does delete all documents correctly.

This is a core bug due to optimization on path: if i'm deleting docs with paths /my/doc/path and /my/doc/path.XXXXXX (XXXX being generated by the core itself to resolve name conflicts), only /my/doc/path will be deleted.