Use the simplevars lens instead of semanage

Because semanage lens was introduced in augeas-lenses 1.12, which might
be not available in target products.

See https://github.com/hercules-team/augeas/pull/594/files

src/lib/cfa/selinux.rb

@@ -60,13 +60,20 @@ def self.load(file_handler: Yast::TargetFile, file_path: PATH)
     #
     # @see CFA::BaseModel#initialize
     def initialize(file_handler: Yast::TargetFile, file_path: PATH)
-      super(AugeasParser.new("semanage.lns"), file_path, file_handler: file_handler)
+      super(AugeasParser.new(LENS), file_path, file_handler: file_handler)
     end
 
     private
 
     # Default path to the SELinux config file
     PATH = "/etc/selinux/config".freeze
     private_constant :PATH
+
+    # The lens to be used by Augeas parser
+    #
+    # @note uses the simplevars lens instead of semanage because the latest is only available from
+    #   augeas-lenses >= 1.12. See https://github.com/hercules-team/augeas/pull/594/files
+    LENS = "simplevars.lns".freeze
+    private_constant :LENS
   end
 end

test/cfa/selinux_test.rb

@@ -41,8 +41,8 @@
   end
 
   describe "#initialize" do
-    it "creates an own Augeas instance" do
-      expect(::CFA::AugeasParser).to receive(:new).with("semanage.lns").and_call_original
+    it "creates an own Augeas instance using simplevars lens" do
+      expect(::CFA::AugeasParser).to receive(:new).with("simplevars.lns").and_call_original
 
       described_class.new(file_handler: file_handler)
     end