caas operatorprovisionerinfo should get agent version from model config

Description of change

fix upgrade caas controller issue (currently, upgrade controller will upgrade caas operators in all models as well)

QA steps

1. bootstrap to k8s
2. creates a caas model and deploys some workloads
3. upgrade controller
4. monitor only controller is upgraded but not operators

Documentation changes

None (bug fix)

Bug reference

bug that has not been released yet.

该提问来源于开源项目：juju/juju