Humility gets the task ordering from the ZIP directory, not the toml

[cbiffle]

More bugs I'm discovering using exhubris tools:

The exhubris tools order the ZIP file entries for the task elf images in elf/task/NAME alphabetically. The original Hubris build system happens to use the TOML declaration order.

It turns out Humility is relying on this in at least some cases for assigning tasks to indices, resulting in a garbled task listing order in commands like tasks (and presumably a misinterpretation of taskids in commands like ipc, but I haven't checked).

The canonical task order is defined in the app.toml file, and this should be the only ordering that's used.