DBaaS: Delete PSMDB cluster action takes too long

User impact:

When user deletes a PSMDB cluster and clicks Proceed, the Confirm action modal hangs there for too long looking like nothing is happening

STR:

Create a PSMDB cluster (with v1.8 operator)
Delete it and confirm

Actual result:

Confirm action stays long

Expected result:

Confirm action should disappear right after confirmation and the cluster status should change to deleting