This code is more generic than it needs to be and one of the side
effects is that an extra init process is forked for odm_init, despite
it having the same context as vendor_init. I don't think anything is
going to change regarding that soon, so this change stops forking that
extra process to save its memory and simplifies the code overall.
Bug: 141164879
Test: init still uses vendor_init for vendor_scripts
Test: init unit tests
Test: init only has one subcontext process
Change-Id: I0d224455604a681711e32f89fb20132378f69060
Now that Result<T> is actually expected<T, ...>, and the expected
proposal states expected<void, ...> as the way to indicate an expected
object that returns either successfully with no object or an error,
let's move init's Result<Success> to the preferred Result<void>.
Bug: 132145659
Test: boot, init unit tests
Change-Id: Ib2f98396d8e6e274f95a496fcdfd8341f77585ee
