Revert "test-server-utils: Disable the cache-reaper in the test environment"

This reverts commit fcdad7cc7779692d6a63d194c55ed3ac1bca0f3c.
EDataBookFactor / EDataBook: Migrated locale handling to EDataBookFactory

The EDataBookFactory is the server side singleton, this is the right
place to handle locale changes, now each EDataBook is set into the
correct locale by the factory, when books are created, and when the
locale change notification arrives.
EBookBackend: Fixed ref-counting bug in e_book_backend_set_locale()
EBookClientCursor: Keep a strong reference to the client

When finalizing a cursor, it is important to have access
to the direct backend available so that it can be asked
to delete the direct access cursor instance.

For this reason EBookClientCursor must keep the EBookClient alive,
EBookClient now exposes a hidden API (not in the header file)
to allow the EBookClientCursor to ask the EBookClient to delete
the cursor on the EBookClientCursor's behalf.

Ugly, but works.
EBookSqlite: Fixed a transaction which wanted to read, but asked to write.