Add CentOS (#12)

* Add CentOS 7

* Fix rawhide boot

* Test locale versions

sources/inputs.pkr.hcl

@@ -65,6 +65,6 @@ locals {
 		username = "vagrant"
 		password = "vagrant"
 		handshake_attempts = 1000
-		timeout = "5h50m"
+		timeout = "5h45m"
 	}
 }

sources/virtualbox-iso.pkr.hcl

@@ -11,6 +11,7 @@ source "virtualbox-iso" "x86_64" {
 	ssh_username = local.ssh.username
 	ssh_password = local.ssh.password
 	ssh_handshake_attempts = local.ssh.handshake_attempts
+	ssh_private_key_file = "vagrant/insecure_key"
 
 	vm_name = "packer-${local.name}"
 	disk_size = "${local.disk_size}000"