For ObjectMeta pruning, we round trip through marshalling and
unmarshalling. If the ObjectMeta contained any strings with "" (or other
fields with empty values) _and_ the respective fields are omitempty,
those fields will be lost in the round trip process.
This makes ObjectMeta after the no-op write different from the one
before the write.
Resource version is incremented every time data is written to etcd.
Writes to etcd short-circuit if the bytes being written are identical
to the bytes already present. So this ends up incrementing the
resourceVersion even on no-op writes.
The zero values are set in BeforeCreate and BeforeUpdate. This commit
updates BeforeUpdate such that zero values are only set when the
object does not have a zero value for the respective field.