- Don't use fixed names for the disks. This will allow us to
parallelize this test.
- Add a new "GETKEY:<key>" String parameter which can retrieve keys
from the handle. The temporary disk names are stored as keys.
- Don't test the close callback. However this uses the close callback
mechanism to delete the temporary disks, and in any case close
callbacks are well tested by the language binding tests.
- The generated code now produces a static array of tests (instead of
a 'perform_tests' function), making it possible to parallelize.