deposit.parsers: Process namespace when using xmltodict.parse

This keeps the existing behavior though by mapping the expanded namespace (full url in keys) to simpler namespaces (again as it is currently).

This also fixes some test data sample which were not properly defining their namespace (and which now expectedly failed).

This will allow to deal properly with all empty body cases (only 1 so far). !385 (closed) fixes that.

Test Plan

tox

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Migrated from D4065 (view on Phabricator)