It was erroneously assumed, that all attributes for input record are
always filled. This may not be the case. When input record only
partially filled, the current settings must be read from the git
backend, without nullifying false values and merged with partially
filled input record. Only after this merging new values can be written
to the git backend.
Change-Id: Iff5763fd408918622d6e82ac122bf09a99d9aaba
ddd8ec8d06