Emulate module loading/unloading in LD_PRELOAD libraries

[evelikov]

Namely: the ld preload shims are not properly managing the relevant sysfs files:

• init_module.c creates /sys/module/xxx/initstate yet lacks .../refcnt and .../holders
• delete_module.c returns success if /sys/module/xxx is missing aka module is not loaded (already unloaded), completely ignores ../refcnt and .../holders.

Originally posted by @evelikov in #393 (comment)

Off the top of my head, this should be enough to test for issues like the one in the link...