Bug 967: Fixed incorrect delete was addressing augmentation of augmentation

DataNormalizationOperation was constructed incorrectly, if augmentation
was already augmented, which leaded to incorrect construction of instance
identifier for delete.

Patchset 2: Fixed normalization in cases of mixin inside mixin
e.g. augmentation containing choice with cases.

Change-Id: I580e5dfe41ce504775ac454b66368037f4d707bb
Signed-off-by: Tony Tkacik <ttkacik@cisco.com>