Reorder the old compatibility arguments

The registration for --os-cert, os-cacert, and os-key were moved
recently into a new method. We need to register the new versions
(which have default values set) before the old compatible versions
(--os_cert, etc.) that have no default values set or the default
values which pull from the env variables (OS_CERT, etc.) get
ignored.

Change-Id: I4bfb89d02909176be420dd978f8235d94978c494
Closes-bug: 1347957