The first page of the create wizard built the next page's URL from a
reversed ".../x86_64/pc/" by replacing "x86_64" with the chosen
architecture and then the first "pc" with the machine type. An
architecture containing "pc" got the machine type inside its name:
ppc64le with pseries went to /instances/create/1/ppseries64le/pc/, so
VMs could not be created on PowerPC hosts.
The URL is now reversed with the placeholders __arch__ and __machine__,
which the script replaces with the URL-encoded values.
The test renders the page, runs the script with node and fails on the
previous template for ppc64le.
