monitor/dim_brightness after suspend (S3) cannot be run on 18.04

[Scott Hu]

CID: 201712-26038
Image: somerville-bionic-amd64-iso-hybrid-20180502-29

Steps:
Run monitor/dim_brightness after suspend (S3) on 18.04 image

Expected result:
test can be run normally

Actual result:
show "Cannot find job with checksum 5b0b159d9a399f704674f1259c515fb9944b086cb515a960bd1c76af339d3d2"

u@u-XPS-13-9370:~$ checkbox-cli -v
INFO:plainbox.config:Loading configuration from ['/etc/xdg/plainbox.conf', '/home/u/.config/plainbox.conf']
INFO:plainbox.secure.providers.v1:Provider initialized com.canonical.ce:oem, version 1.0
INFO:plainbox.secure.providers.v1:Provider initialized certification-client, version 0.33.0
INFO:plainbox.secure.providers.v1:Provider initialized plainbox-provider-checkbox, version 0.44.0
INFO:plainbox.secure.providers.v1:Provider initialized plainbox-provider-resource-generic, version 0.36.0
INFO:plainbox.secure.providers.v1:Provider initialized plainbox-provider-tpm2, version 1.7.0
INFO:plainbox.secure.providers.v1:Provider initialized com.canonical.plainbox:manifest, version 1.0
INFO:plainbox.secure.providers.v1:Provider initialized com.canonical.plainbox:exporters, version 1.0
INFO:plainbox.secure.providers.v1:Provider initialized com.canonical.plainbox:categories, version 1.0