Vagrantfile: update to Fedora 28

Signed-off-by: Giuseppe Scrivano <[email protected]>

Vagrantfile

@@ -1,13 +1,13 @@
 # -*- mode: ruby -*-
 # vi: set ft=ruby :
 #
-#  The fedora/25-cloud-base and debian/jessie64 boxes are also available for
+#  The fedora/28-cloud-base and debian/jessie64 boxes are also available for
 #  the "virtualbox" provider.  Set the VAGRANT_PROVIDER environment variable to
 #  "virtualbox" to use them instead.
 #
 Vagrant.configure("2") do |config|
   config.vm.define "fedora" do |c|
-    c.vm.box = "fedora/25-cloud-base"
+    c.vm.box = "fedora/28-cloud-base"
     c.vm.synced_folder ".", "/vagrant", type: "rsync",
       rsync__exclude: "bundles", rsync__args: ["-vadz", "--delete"]
     c.vm.provision "shell", inline: <<-SHELL