init_kill_services_test: reboot device first.

This test is killing critical device services, and if it runs
repeatedly or some of the critical services have already died, it'll
force the device to reboot again and potentially consider the test a
failure.

This forces the test to reboot first, so that it is in a fresh state and
we can avoid this type of flake on the device.

Bug: 153444614
Test: atest init_kill_services_test
Change-Id: Ia81a319af1d209f58e70f824bb8eb7f11973637c