Fix augment/deviate mechanics
Parsing of YANG models with a deviation fails if the deviation target
node is conditionally augmented based on a feature.
The problem is we are reusing are reusing setUnsupported() for two
cases: when the feature is not supported and when the target is not
available.
Separate the second case into a separate boolean, and if the target is
available, propagate children to target as unsupported -- which makes
namespace resolution work correctly and deviate properly sees the
children as unsupported.
JIRA: YANGTOOLS-1485
Change-Id: I954185dd0067667faae8073e222f07b65907e675
Signed-off-by: Sangwook Ha <sangwook.ha@verizon.com>
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>