Drop vagrant support

Nobody in the development team has ever really used that, it needs a ton
of dependencies, and doesn't work in toolbox/Silverblue. Vagrantfile has
not been updated for a long time (Fedora 29 is EOL).

Our own image-prepare/vm-run/image-customize etc. machinery is efficient
enough, and proven to work.

Closes #14369

HACKING.md

@@ -206,35 +206,6 @@ You need to disable SELinux with
 for this to work, as your local build tree does not otherwise have the expected
 SELinux type.
 
-## Working on Cockpit using Vagrant
-
-It is also possible to use a Vagrant virtual machine to develop Cockpit.
-
-Most of Cockpit is written in JavaScript. Almost all of this code is found
-in the packages in the pkg/ subdirectory of the Cockpit git checkout.
-
-To use Vagrant to develop Cockpit, run in its top level git checkout.
-In some cases you may need to use `sudo` with vagrant commands:
-
-    $ vagrant up
-
-Now you can edit files in the `pkg/` subdirectory of the Cockpit sources.  Use
-`make` to build those sources. The changes should take effect after syncing
-them to the Vagrant VM. For example:
-
-    $ make && vagrant rsync
-
-Now log into Cockpit on the vagrant VM to see your changes. Use the
-user name 'admin' and the password 'foobar' to log in. The Cockpit
-instance in vagrant should be available at the following URL:
-
-http://localhost:9090
-
-If you want to setup automatic syncing as you edit JavaScript files
-you can run:
-
-    $ vagrant rsync-auto &
-
 ## Installation from upstream sources
 
     $ make

Vagrantfile

@@ -1,69 +0,0 @@
-# vi: set ft=ruby :
-#
-# See HACKING.md for how to use this Vagrantfile.
-#
-
-Vagrant.configure(2) do |config|
-
-    config.vm.box = "fedora/29-cloud-base"
-    config.vm.synced_folder ".", "/vagrant", disabled: true
-    config.vm.synced_folder "./dist", "/cockpit/dist", type: "rsync", create: true, rsync__args: ["--verbose", "--archive", "--delete", "-z"]
-    config.vm.network "private_network", ip: "192.168.50.10"
-    config.vm.network "forwarded_port", guest: 9090, host: 9091
-    config.vm.hostname = "cockpit-devel"
-    config.vm.post_up_message = "You can now access Cockpit at http://localhost:9090 (login as 'admin' with password 'foobar')"
-
-    config.vm.provider "libvirt" do |libvirt|
-        libvirt.memory = 1024
-        libvirt.nested = true
-        libvirt.cpu_mode = "host-model"
-    end
-
-    config.vm.provider "virtualbox" do |virtualbox|
-        virtualbox.memory = 1024
-    end
-
-    config.vm.provision "shell", inline: <<-SHELL
-        set -eu
-
-        dnf update -y
-        dnf install -y util-linux-user   # for chfn
-
-        echo foobar | passwd --stdin root
-        getent passwd admin >/dev/null || useradd -c Administrator -G wheel admin
-        echo foobar | passwd --stdin admin
-
-        usermod -a -G wheel vagrant
-        chfn -f Vagrant vagrant
-
-        mkdir -p /root/.local/share /home/admin/.local/share /usr/local/share
-        ln -snf /cockpit/dist /usr/local/share/cockpit
-        ln -snf /cockpit/dist /root/.local/share/cockpit
-        ln -snf /cockpit/dist /home/admin/.local/share/cockpit
-
-        dnf copr enable -y @cockpit/cockpit-preview
-        dnf install -y \
-            atomic \
-            docker \
-            etcd \
-            firewalld \
-            git \
-            NetworkManager \
-            pcp \
-            qemu \
-            realmd \
-            storaged \
-            storaged-lvm2 \
-            subscription-manager \
-            tuned libvirt \
-            yum-utils
-        dnf install -y cockpit
-
-        systemctl enable cockpit.socket
-        systemctl start cockpit.socket
-
-        printf "[WebService]\nAllowUnencrypted=true\n" > /etc/cockpit/cockpit.conf
-
-        systemctl daemon-reload
-    SHELL
-end