Juju does not spin up new pod after charm upgrade as it is unable to mount config map

To reproduce (on juju 2.8):

$ juju bootstrap microk8s mk8s
$ juju add-model t1
$ juju deploy cs:~charmed-osm/prometheus-6

# Wait for the charm to settle and upgrade to revision 7 which includes a new config map
$ juju upgrade-charm prometheus

If you tail `kubectl -n t1 get pods` you will notice that the existing pods get terminated but no new pods spin up. In the logs you will notice entries like "create Pod prometheus-0 in StatefulSet prometheus failed error: Pod "prometheus-0" is invalid: spec.containers[1].volumeMounts[3].name: Not found: "web-config"".

Interestingly, removing the application and redeploying the latest charm does not work unless you `juju remove prometheus --destroy-storage` to get rid of the allocated PV.