This issue is resolved in vCenter server 7.0 U3h or higher versions.
Please refer to : VMware vCenter Server 7.0 Update 3h Release Notes
Workaround:
This workaround can be applied either at vCenter Server 7.0u3f itself that is the failed state or vCenter Server 7.0u3d which is before starting upgrading to 7.0u3f.
1. Connect to vCenter Server SSH session with root credentials.
2. Connect to WCP database using the below command:
3. Run the following command to check the entries that have instance_id as null:
4. Update the instance_id in cluster_db_configs to random UUID where it is null:
5. WCP service (and any other service that has not started after the upgrade) needs to be restarted once the DB entry has been fixed.
6. Re-run Step 2 and 3 to verify instance_id is not NULL. Now vCenter Server must be up and running.
7. At this stage if the user have applied this workaround at vCenter Server 70u3d, then proceed upgrading to vCenter Server 70u3f or If the user has applied the workaround at vCenter Server 70u3f, then visit the VMware Appliance Management Interface (VAMI) or CLI installer and resume the upgrade.