Comment 1 for bug 1800730

The interface-mysql-shared may need to unset the following on shared-db departed:

shared-db.available
shared-db.connected
db.synched

Triage:

Handle the case:
juju remove-relation $REACTIVE_CHARM mysql

Determine if the departed hook is the last unit in the shared-db relation
If so, unset all flags pertaining to the shared-db relation