Make the impl::is_abortable() return 'yes' and check the impl::_as in
the files listing loop. It's not real abort, since files listing loop is
expected to be fast and most of the time will be spent in s3::client
code reading data from disk and sending them to S3, but client doesn't
support aborting its requests. That's some work yet to be done.
Also add injection for future testing.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
ed6e6700ab