ssh.kttp_alive: Add option to add the ssh keep alive option

We have an issue where sometimes the ssh connection is killed.  this
happens due to puppet changing the sshd keep alive settings while beaker
is still running.

This patch adds the ability for users to add ssh_keep_alive to the host
config to ensure we send keep alive packets every 5 seconds

lib/beaker/hypervisor/vagrant.rb

@@ -53,6 +53,7 @@ def make_vfile(hosts, options = {})
       hosts.each do |host|
         host.name.tr!('_', '-') # Rewrite Hostname with hyphens instead of underscores to get legal hostname
         set_host_default_ip(host)
+        v_file << "  c.ssh.keep_alive = true\n" if host['ssh_keep_alive'] == true
         v_file << "  c.vm.define '#{host.name}' do |v|\n"
         v_file << "    v.vm.hostname = '#{host.name}'\n"
         v_file << "    v.vm.box = '#{host['box']}'\n"

spec/beaker/vagrant_spec.rb

@@ -103,6 +103,16 @@ module Beaker
       expect(vagrantfile).to match(/(ssh.forward_agent = true)/)
     end
 
+    it 'can make a Vagrantfile with ssh timeout' do
+      path = vagrant.instance_variable_get(:@vagrant_path)
+
+      hosts = make_hosts({ssh_keep_alive: true}, 1)
+      vagrant.make_vfile(hosts, options)
+
+      vagrantfile = File.read(File.expand_path(File.join(path, 'Vagrantfile')))
+      expect(vagrantfile).to match(/(ssh.keep_alive = true)/)
+    end
+
     it 'can replace underscores in host.name with hypens' do
       path = vagrant.instance_variable_get(:@vagrant_path)