Table.pm in a refresh scenario with cache not currently in use, but existing none the less, mark the cache as invalid by setting the timestamp to 1970

Still avoid *rebuilding* the cache, as in the use_cache not set suggests a mass amount of setAttribs and build_cache(1) would be extremely expensive,
just force the next consumer after the set to take the hit

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/branches/2.7@14002 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

perl-xCAT/xCAT/Table.pm

@@ -2108,6 +2108,8 @@ sub _refresh_cache { #if cache exists, force a rebuild, leaving reference counts
                     #   (uses stale nodelist data and misses new nodes, the error)
                     #1st noderange finishes
                     #2nd noderange finishes
+    } else { #even if a cache is not in use *right this second*, we need to mark any cached data that may exist as invalid, do so by suggesting the cache is from 1970
+	if ($self->{_cachestamp}) { $self->{_cachestamp}=0; }
     }
     return;
 }