Fix be_installed matcher when used with expect

When used like

  expect(package('httpd')).to be_installed

it causes an error that subject is not defined

  undefined local variable or method `subject' for
  #<RSpec::Matchers::DSL::Matcher be_installed> (NameError)

It should be changed to use the passed #match parameter 'name'
instead of 'subject'.

lib/serverspec/matcher/be_installed.rb

@@ -1,6 +1,6 @@
 RSpec::Matchers.define :be_installed do
   match do |name|
-    if subject.class.name == 'Serverspec::Type::SelinuxModule'
+    if name.class.name == 'Serverspec::Type::SelinuxModule'
       name.installed?(@version)
     else
       name.installed?(@provider, @version)