CRM-17842 hook_custom called twice for custom field on address

hook_custom seems to be called twice after saving information to a custom field that is attached to the address entity.

Steps to recreate:

• Add a custom field to addresses
• Create a hook implementation that prints the params when the hook is called
• Add an address, adding a value to the custom field
• View the printed params, notice that the hook imeplementation is called twice, with slightly different params (screenshot attached)