lava_dispatcher_host: fix device sharing with cgroups v1

That missing return statement caused lava-dispatcher-host.service to
crash when responding to requests.
19 jobs for fix-cgroups-v1 in 16 minutes and 38 seconds (queued for 7 seconds)
Status Name Job ID Coverage
  Test
passed dispatcher-debian-10 #146084
amd64

00:02:28

passed dispatcher-debian-11 #146086
amd64

00:02:28

passed server-debian-10 #146085
amd64

00:03:00

passed server-debian-11 #146087
amd64

00:05:10

 
  Analyze
passed bandit-sast #146088
amd64-dind

00:00:57

passed black #146091
amd64

00:00:43

passed code_quality #146092
amd64

00:00:23

passed codespell #146097
amd64

00:00:20

passed coverage #146093
amd64

00:06:58

60.93%
passed dockerfiles #146094
amd64

00:00:17

passed eslint-sast #146089
amd64-dind

00:00:25

passed pylint #146096
amd64

00:02:37

passed schemas #146095
amd64

00:00:31

passed semgrep-sast #146090
amd64-dind

00:01:02

 
  Build
passed debian/10 #146099
amd64

00:01:36

passed debian/11 #146100
amd64

00:01:34

passed doc #146098
amd64

00:00:41

passed docker-amd64-dispatcher #146101
amd64-dind

00:03:57

passed docker-amd64-server #146102
amd64-dind

00:04:21