init: Add support for ${x.y:-default} expansion

commit 00ede7d2626f9343d330dc6f5286bba3e99e41d0 (init: do
expand_props before calling the builtins) broke logpersist

Bug: 28120456
Bug: 22654233
Bug: 28788401
Change-Id: Ib4d8231665b26ac083b02243177493fab41c8978
1 file changed