Memory leak on recursive unresolved promises.

[Istar-Eldritch]

We use recursive promises in a couple places in the amqp backend. (setup and register functions). We should check if we have to trampoline them.

From the top of my head Iris only uses this recursion to keep the connection alive, thou only increasing the stack on connection loss. This means that the memory leaked in iris is negligible as the number of times the connection needs to drop for this to be noticeable it's likely to be never reached. (2-3Mb every 10k recursive calls)

Background and relevant links:
This problem was spotted while writing a new data transfer tool that was using recursive pagination to call the database using promises over Iris. The main issue was not in iris but the recursive call itself.

• chain of never resolved promises create memory leaks promises-aplus/promises-spec#179
• https://mail.mozilla.org/pipermail/es-discuss/2015-April/042517.html