Convert objectstorage-role.yaml to role.role.j2.yaml

Convert objectstorage-role.yaml to role.role.j2.yaml

Add some special-casing for backwards compatibility, such that the
ObjectStorage role can be rendered via j2 for support of composable networks.

Change-Id: I52abbefe2f5035059ccbed925990faab020c6c89
Partially-Implements: blueprint composable-networks