fixed Python 3 keys() usage (#1861)

* fixed python3 keys()

* added changelog fragment

* Update plugins/modules/cloud/spotinst/spotinst_aws_elastigroup.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update plugins/cache/redis.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* rolledback redis.py per PR

* Update plugins/modules/monitoring/sensu/sensu_check.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* removed unnecessary ignore lines

* adding memcached and one case in redis is indeed necessary

* Update changelogs/fragments/1861-python3-keys.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

* Update changelogs/fragments/1861-python3-keys.yml

* Update changelogs/fragments/1861-python3-keys.yml

Co-authored-by: Felix Fontein <felix@fontein.de>

Co-authored-by: Felix Fontein <felix@fontein.de>

plugins/modules/cloud/lxd/lxd_container.py

@@ -665,7 +665,7 @@ def main():
                 type='dict',
             ),
             state=dict(
-                choices=LXD_ANSIBLE_STATES.keys(),
+                choices=list(LXD_ANSIBLE_STATES.keys()),
                 default='started'
             ),
             target=dict(