Check that a product variable is set

Store product variables in pointers so that we can only apply the
properties if the product variable was set to a value.  Also only apply
bool properties if they are true, adn rearrange the code to do the
cheapest checks first.

Remove device_uses_logd, it doesn't exist any more.

Change-Id: Icf42408f57bd611746f8d985bfceb50c7f95ea59
1 file changed