The WebDAV backends contained a hack where the UID inside the data was forced
to be identical to the resource name. This is wrong for items created by us
via POST (because the server may choose a resource name != UID) or by some
other entity (where we have no idea how the resource name got chosen).
This commit removes the hack. Testing must be updated to pass correct data
with the same UID as on the server when updating an item, because the backend
will no longer ensure that and changing the UID of a resource gets rejected by
some servers.
The hack was introduced for peers which do not store the UID (for example, a
vCard or iCalendar 1.0 based SyncML client). A better solution must be found,
probably involving the Synthesis engine and its read/update/write cycle.
27af370ac2