Merged patch series by By Benny Halevy:
Prepare for updating seastar submodule to a change
that requires deferred actions to be noexcept
(and return void).
Test: unit(dev, debug)
* tag 'deferred_action-noexcept-v1' of github.com:bhalevy/scylla:
everywhere: make deferred actions noexcept
cql3: prepare_context: mark methods noexcept
commitlog: segment, segment_manager: mark methods noexcept
everywhere: cleanup defer.hh includes
d598a94b43