GUnixSocketAddress: fix construct parameter issue
GUnixSocketAddress: fix construct parameter issue

GUnixSocketAddress has some very strange logic for interpreting its
construct paramters.  This logic behaves differently in these two cases:

  g_object_new (G_TYPE_UNIX_SOCKET_ADDRESS,
                "abstract", FALSE,
                "address-type", ...,
                NULL);

and

  g_object_new (G_TYPE_UNIX_SOCKET_ADDRESS,
                "address-type", ...,
                NULL);

even though the default value for "abstract" is already FALSE.

Change the way the code works so that it is not sensitive to people
merely setting a property to its default value.

https://bugzilla.gnome.org/show_bug.cgi?id=698686

endlessm/glib,mzabaluev/glib,Distrotech/glib,Distrotech/glib,tchakabam/glib,cosimoc/glib,cention-sany/glib,cention-sany/glib,cention-sany/glib,johne53/MB3Glib,endlessm/glib,tchakabam/glib,tamaskenez/glib,tamaskenez/glib,MathieuDuponchelle/glib,mzabaluev/glib,Distrotech/glib,johne53/MB3Glib,krichter722/glib,tchakabam/glib,gale320/glib,cosimoc/glib,tamaskenez/glib,mzabaluev/glib,endlessm/glib,ieei/glib,MathieuDuponchelle/glib,endlessm/glib,cosimoc/glib,krichter722/glib,lukasz-skalski/glib,MathieuDuponchelle/glib,lukasz-skalski/glib,tamaskenez/glib,cention-sany/glib,ieei/glib,tchakabam/glib,cosimoc/glib,tchakabam/glib,mzabaluev/glib,gale320/glib,ieei/glib,ieei/glib,gale320/glib,gale320/glib,endlessm/glib,krichter722/glib,johne53/MB3Glib,lukasz-skalski/glib,krichter722/glib,johne53/MB3Glib,cention-sany/glib,johne53/MB3Glib,tamaskenez/glib,gale320/glib,krichter722/glib,lukasz-skalski/glib,johne53/MB3Glib,mzabaluev/glib,MathieuDuponchelle/glib,Distrotech/glib,lukasz-skalski/glib,cosimoc/glib,ieei/glib,MathieuDuponchelle/glib,Distrotech/glib