Commit aafb21a0 "qobject: let object_property_get_str() use new API"
isn't much of a simplification.  Not worth having
object_property_get_str() differ from the other
object_property_get_FOO().  Revert.

This reverts commit aafb21a0.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Daniel P. Berrangé <berrange@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20201211171152.146877-12-armbru@redhat.com>
Reviewed-by: Eduardo Habkost <ehabkost@redhat.com>