Add err_msg param to baremetal_deploy_helper.
Add err_msg param to baremetal_deploy_helper.

Updates the baremetal-deploy-helper so that we look for an
option 'e' POST parameter which contains an optional error
message string from the agent.

This works with the associated DIB branch here:
  http://review.openstack.org/#/c/33341/

And is also fully backwards compatible with existing agent scripts
which do not send the 'e' parameter.

Change-Id: I9e6766560a8d8bf0d33059fc2547cbb8d2f861f6

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