qubes-anaconda-addon, conf: update to Fedora 28 template

QubesOS/qubes-issues#4013

qubes-anaconda-addon/firstboot-qubes-text

@@ -104,7 +104,7 @@ if [ "$vms_template" == "yes" ]; then
         qvm-shutdown --wait $template
     done
 
-    qubes-prefs --set default-template 'fedora-26'
+    qubes-prefs --set default-template 'fedora-28'
 fi
 
 if [ "$vms_service" == "yes" -o "$vms_app" == "yes" ]; then

qubes-anaconda-addon/org_qubes_os_initial_setup/gui/spokes/qubes_os.py

@@ -228,7 +228,7 @@ class QubesOsSpoke(FirstbootOnlySpokeMixIn, NormalSpoke):
 
         self.qubes_user = None
         self.qubes_gid = None
-        self.default_template = 'fedora-26'
+        self.default_template = 'fedora-28'
 
         self.set_stage("Start-up")
         self.done = False

qubes-release/comps-qubes.xml

@@ -1398,7 +1398,7 @@
       <packagereq type="mandatory">qubes-gui-dom0</packagereq>
       <packagereq type="mandatory">qubes-desktop-linux-manager</packagereq>
       <packagereq type="mandatory">qubes-mgmt-salt-dom0</packagereq>
-      <packagereq type="mandatory">qubes-template-fedora-26</packagereq>
+      <packagereq type="mandatory">qubes-template-fedora-28</packagereq>
       <packagereq type="default">qubes-gpg-split-dom0</packagereq>
       <packagereq type="default">qubes-img-converter-dom0</packagereq>
       <packagereq type="default">qubes-input-proxy</packagereq>