Panic when dropping RawTask

[ozgrakkurt]

Panic happens here:

glommio/glommio/src/task/raw.rs

Line 351 in d3f6e7a

let refs = Self::decrement_references(&*(raw.header as *mut Header));

I couldn't get a stack trace because the issue happened on production configuration. Will have more info if it happens again.

Couldn't find a reproducer yet. I'll manually check the code a bit to see if I can find something.

[ozgrakkurt]

Also maybe the executor can contain the panics and not crash itself? For now I just made it abort the process if one of the executors crash because of panic.

[ozgrakkurt]

Seems like this is very similar to #379

Curious if it is possible to remove the c style code from this area and just use Arc