Fixed variable check and dns error handling in nsupdate script.

dns/templates/nsupdate.sh.erb

@@ -1,7 +1,7 @@
 #!/bin/sh
 
 DNSSERVER="<%= dns_nsupdate_server -%>"
-DNSZONE="<% if defined?(dns_nsupdate_zone) -%><%= dns_nsupdate_zone -%><% end %>"
+DNSZONE="<% if has_variable?("dns_nsupdate_zone") -%><%= dns_nsupdate_zone -%><% end %>"
 MYNAME="<%= dns_nsupdate_name -%>"
 MYKEY="<%= dns_nsupdate_key -%>"
 
@@ -24,7 +24,7 @@ esac
 
 
 # try to get current addr/name from dns
-CURADDR=`dig +noall +answer @${DNSSERVER} ${MYNAME} A | awk '{ print $5 }'`
+CURADDR=`dig +short @${DNSSERVER} ${MYNAME} A 2>/dev/null`
 if [ $? -ne 0 ]; then
     # we should get this only in dns errors so exit quietly
     exit 1
@@ -32,7 +32,7 @@ fi
 
 
 # exit now if we are up to date
-if [ ${CURADDR} = ${MYADDR} ]; then
+if [ "${CURADDR}" = "${MYADDR}" ]; then
     exit 0
 fi