Fix missed exception raise in _add_driver_fields
Fix missed exception raise in _add_driver_fields

There was a bug where the NovaException was not being raised in
the IronicDriver._add_driver_fields() method if the client update
call failed after the maximum number of retries.

Change-Id: Ic082079f35892cc2bf3fcad46cd33cebd1105608

naterh/ironic,faizan-barmawer/openstack_ironic,hpproliant/ironic,pshchelo/ironic,froyobin/ironic,dims/ironic,JioCloud/ironic,rdo-management/ironic,ramineni/myironic,bacaldwell/ironic,Tehsmash/ironic,SauloAislan/ironic,rackerlabs/ironic,supermari0/ironic,Tan0/ironic,openstack/ironic,redhat-openstack/ironic,dims/ironic,varunarya10/ironic,SauloAislan/ironic,naototty/vagrant-lxc-ironic,debayanray/ironic_backup,naototty/vagrant-lxc-ironic,devananda/ironic,ionutbalutoiu/ironic,ionutbalutoiu/ironic,pshchelo/ironic,openstack/ironic,NaohiroTamura/ironic,NaohiroTamura/ironic,bacaldwell/ironic