All the active users of mounts.h now live in updater/.
Test: mmma bootable/recovery
Test: Run recovery_unit_test on taimen.
Test: Code search shows no reference to otautil/mounts.h in device dirs.
Change-Id: I6c35d2e403e92a0111102d00aa4773f4f524650e
Export its header (mounts.h) from there, and drop the dot dot dependency
from libupdater / updater.
Test: mmma bootable/recovery
Test: recovery_component_test
Change-Id: Ic26a6b9b78a34dbe1f178b138f3abaafffbec44c