test: improve macro-hooks patch

Restore aio_max_nr to its original value when unloading.

Also move the location of the patch hunk to be not at the end of the
file.  Otherwise we hit a weird combinediff bug which results in the
diff's context being removed.
make "descriptor" a special static local variable

The "descriptor" static local variables and their containing __verbose
section are used for dynamic debug printks.  They should be considered
as special static local variable symbols because they have the same
requirements: they should never be correlated and they should only be
included if referenced by an included function.
Merge pull request #436 from jpoimboe/descriptor

make "descriptor" a special static local variable