Fix check mode for grafana role

[Boschung-Mecatronic-AG-Infrastructure]

The current main code does not support --check mode.
It does errors:

TASK [grafana.grafana.grafana : Import grafana dashboards] *********************
fatal: [host]: FAILED! => {"msg": "'dict object' has no attribute 'path'. 'dict object' has no attribute 'path'"}
TASK [grafana.grafana.grafana : Remove dashboards not present on deployer machine (synchronize)] ***
fatal: [host]: FAILED! => {"msg": "Invalid data passed to 'loop', it requires a list, got this instead: set(). Hint: If you passed a list/dict of just one element, try adding wantlist=True to your lookup invocation or use q/query instead of lookup."}

Proposed modifications make --check option running smoothly without any errors.

[CLAassistant]

All committers have signed the CLA.