(MODULES-1570) Add java_major_version fact

Gives the major version of the Java release (ie. Java 1.7.0_71, major version is 7)

We also want to specifically return nil when java not present

lib/facter/java_patch_level.rb

@@ -13,10 +13,6 @@
 Facter.add(:java_patch_level) do
   setcode do
     java_version = Facter.value(:java_version)
-    if java_version.nil?
-      "JAVA_NOT_INSTALLED"
-    else
-      java_patch_level = java_version.strip.split('_')[1]
-    end
+    java_patch_level = java_version.strip.split('_')[1] unless java_version.nil?
   end
 end