start_osds: Use list instead of keys

start_osds: Use list instead of keys

If you use python3 based ansible then keys() returns a dict_keys object,
not a list of keys. This breaks the installation on such a system. Using
the list filter provides a more robust solution that should work on both
python2 and python3 based ansible. You can find some more information
about the issue, here:

https://github.com/ansible/ansible/issues/19514

Signed-off-by: Boris Ranto <branto@redhat.com>