Order of the class parameters is refactored

Order and intendation of those parameters are changed
to follow Puppet Style Guide recommendation [0].
Moreover, it will allow to an user to find much faster
a variable in a list of variables.

[0]. https://docs.puppetlabs.com/guides/style_guide.html

Change-Id: I1a46fea86c378127fd2f50af49758a8f2007381b

manifests/init.pp

@@ -15,8 +15,8 @@
 # == Class: diskimage_builder
 #
 class diskimage_builder (
-  $use_git = false,
   $git_source_repo = 'git+https://git.openstack.org/openstack/diskimage-builder',
+  $use_git         = false,
   ) {
   include ::pip
   include ::apt