Add comment to ipmi.pm fru process explanation

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@2222 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

xCAT-server/lib/xcat/plugins/ipmi.pm

@@ -2160,7 +2160,8 @@ sub formfru {
     }
     #xCAT will always have a product FRU in this process
     $bytes[4]=$availindex;
-    unless (defined $fruhash->{product}) {
+    unless (defined $fruhash->{product}) { #Make sure there is a data structure
+                        #to latch onto..
         $fruhash->{product}={};
     }
     my @prodbytes = buildprodfru($fruhash->{product});