qemu: Convert from shorthand to longer throttling names

qemu: Convert from shorthand to longer throttling names

We're about to add 6 new options and it appears (from testing) one cannot
utilize both the shorthand (alias) and (much) longer names for the arguments.
So modify the command builder to use the longer name and of course alter the
test output .args to have the similarly innocuous long name.

Also utilize a macro to build that name makes it so much more visually
appealing and saves a few characters or potential cut-n-paste issues.

Signed-off-by: John Ferlan <jferlan@redhat.com>