Forbid removing all /etc/hosts entries from DNS with makedns -d as it pretty well corrupts most configs

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@9983 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

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

@@ -241,6 +241,11 @@ sub process_request {
     } elsif ($allnodes) {
         #read all nodelist specified nodes
     } else { 
+	if ($deletemode) {
+		#when this was permitted, it really ruined peoples' days
+		xCAT::SvrUtils::sendmsg([1,"makedns -d without noderange or -a is not supported"],$callback); 
+		return;
+	}
         #legacy behavior, read from /etc/hosts
         my $hostsfile;
         open($hostsfile,"<","/etc/hosts");