Fixes a KeyError crash in _find_schema_property when traversing
schemas that use 'oneOf' without an explicit 'type' (e.g. server
list/detail response schemas). The bare except block silently
swallowed this crash, causing api-ref description merging to fail
for affected operations and producing non-deterministic YAML output
due to Python hash-seed dependent schema ordering.
Change-Id: I8599cd8c907dd73cea98bde9b43dddb023e71530
Signed-off-by: Artem Goncharov <artem.goncharov@gmail.com>