init: Apply the NormalIoProfile when creating a service

Prepare for migration of the blkio controller to the v2 cgroup hierarchy
by applying the NormalIoProfile when starting a service. While the
NormalIoProfile is automatically applied when the blkio controller is
mounted in the v1 hierarchy, this is not the case for the v2 hierarchy.

Bug: 213617178
Change-Id: I3cad288a31aa2692e10c778ae1e5fdd04acd66d7
Signed-off-by: Bart Van Assche <bvanassche@google.com>