Storage service uses group0 internally, but group0 is create long after
storage service is initialized and passed to it using ss::set_group0()
function. What it means is that during shutdown group0 is destroyed
before ss::stop() is called and thus storage service is left with a
dangling reference. Fix it by introducing a function that cancels all
group0 operations and waits for background fibers to complete. For that
we need separate abort source for group0 operation which the patch
series also introduces.
* 'gleb/group0-ss-shutdown' of github.com:scylladb/scylla-dev:
storage_service: topology coordinator: ignore abort_requested_exception in background fibers
storage_service: fix de-initialization order between storage service and group0_service
52ae6b8738