Make swift tempurl key secret
Make swift tempurl key secret

This prevents the key from being printed out to logs when e.g.
`log_opt_values` is called.

Change-Id: I7c7f8987a467476f4d56fa76c6a35c88561d6858

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