vport_trigger: Fix property name for gsi compatibility.

When running a gsi image, init goes from silently allowing all
properties, to explicitly blocking any property triggers which are not
from a whitelist. Prefixing a property with 'vendor.' is allowed, but
'sys.cf.' is not.

For now, set both the old and new property names for backwards
compatibility. (It is not disallowed to set these properties, just init
won't read them.)

Bug: 110097226
Change-Id: Ie5276b372f6aaf3ba7384256b5911cf0c05d9a81