'View only' custom field on address entity cannot be updated by API

If you attach a 'View only' custom field to the 'address' entity then it cannot be updated by the API.

Normally 'view only' custom fields attached to contacts can be updated via the API.

Steps to recreate on dmaster:

• New custom field set 'fishbone', used for 'Addresses'
• New custom field 'sword': alphanum text, active, view only
• Find the address ID of an address on the demo record
• Using the API explorer, create an 'Address: Create' action:
• - Address ID: as discovered
• - sword: excalibur
• - execute
• Note that the custom field value has not been added to the address

• Edit the custom field, to make it not 'view only'
• Execute the API call again
• Note that the custom field value HAS been added to the address