Fix uses/augment linkage

Fix uses/augment linkage

Our previous fix for MDSAL-715 switched the resolution logic to a unified
approach based on linked augmentation. Unfortunately it missed the fact
that linking the groupings also had the side-effect of setting the
augment target, which in turn populates 'augments' list.

Our failure to do so ends up wrecking lookups in the case where we have
an uses-augmented node further augmented by a module-augment.

Fix this by intertwining original and augment linkage, so that a subtree
root (such as module) pays attention to augments which need to resolve
before descending to recursive linkage.

JIRA: MDSAL-718
Change-Id: I7bd6cbed636267d35113888ddd35f0c6d9411043
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>