Explicitly enable firstboot in the desktop kickstarts

This ensures that gnome-initial-setup will run in user mode on
first login as 'test' user for F26+, as it did for <=F25 and as
the tests expected (we can now remove the workaround I added
because this stopped happening with F26). Bump the image version
so the images get rebuilt.

desktop.ks

@@ -10,6 +10,7 @@ clearpart --all
 autopart
 rootpw --plaintext weakpassword
 user --name=test --password=weakpassword --plaintext
+firstboot --enable
 poweroff
 
 %packages

desktopencrypt.ks

@@ -10,6 +10,7 @@ clearpart --all
 autopart --encrypted --passphrase=weakpassword
 rootpw --plaintext weakpassword
 user --name=test --password=weakpassword --plaintext
+firstboot --enable
 poweroff
 
 %packages

hdds.json

@@ -140,7 +140,7 @@
                 "branched": ["x86_64"]
             },
             "size" : "20",
-            "imgver": "3",
+            "imgver": "4",
             "variant": "Workstation"
         },
         {