get ip addr with getent

Build kdump image will fail when kdump.conf has net option with a host name
instead of ip address.

Handle this just as what we do in rhel6: use getent to get the ip addr.

Signed-off-by: Dave Young <dyoung@redhat.com>

kdump_dracut_modules/99kdumpbase/module-setup.sh

@@ -57,6 +57,9 @@ install() {
                 _server=$(echo $config_val | sed -e 's#\(.*\):.*#\1#')
             fi
 
+            _need_dns=`echo $_server|grep "[a-zA-Z]"`
+            [ -n $need_dns ] && _server=`getent hosts $_server|cut -d' ' -f1`
+
             _netdev=`/sbin/ip route get to $_server 2>&1`
             [ $? != 0 ] && echo "Bad kdump location: $config_val" && exit 1
             #the field in the ip output changes if we go to another subnet