Cleanly shut down daemon

[haadcode]

Currently the daemon doesn't shut down cleanly due to:

• Open object.get requests when killing the daemon
• Open pubsub subscscriptions

This is due to js-ipfs-spi being on the main process and we don't "reload" it when shutting down the daemon.

A good solution here would be to fix the issues directly in js-ipfs-api so that all state is per instance (and doesn't leak through like it does now).