add dnshandler def in Schema

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/trunk@10198 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd

perl-xCAT/xCAT/Schema.pm

@@ -784,6 +784,7 @@ site => {
    "                       mn|eth1,eth2;service|bond0.\n\n".
    " dhcpsetup:  If set to 'n', it will skip the dhcp setup process in the nodeset cmd.\n\n".
    " disjointdhcps:  If set to '1', the .leases file on a service node only contains\n".
+   " dnshandler:  Name of plugin that handles DNS setup for makedns.\n".
    "                 the nodes it manages. The default value is '0'.\n\n".
    " domain:  The DNS domain name used for the cluster.\n\n".
    " ea_primary_hmc:  The hostname of the HMC that the Integrated Switch Network\n".