rados.cc: fix pool alignment check

io_ctx is initialized iff pool_name.

Introduced in 304b08a23a3db57010078046955a786fe3589ef8
Fixes: #8652
Signed-off-by: Samuel Just <sam.just@inktank.com>
Merge remote-tracking branches 'origin/wip-7999-master', 'origin/wip-8396', 'origin/wip-8438-master', 'upstream/next' and 'upstream/wip-fix-rados-tool' into wip-sam-testing