fixed Python 3 keys() usage (#1861) (#1891)

* 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>
(cherry picked from commit 434f383ae9)

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

plugins/modules/cloud/lxc/lxc_container.py

@@ -1662,7 +1662,7 @@ def main():
             ),
             backing_store=dict(
                 type='str',
-                choices=LXC_BACKING_STORE.keys(),
+                choices=list(LXC_BACKING_STORE.keys()),
                 default='dir'
             ),
             template_options=dict(
@@ -1699,7 +1699,7 @@ def main():
                 type='path'
             ),
             state=dict(
-                choices=LXC_ANSIBLE_STATES.keys(),
+                choices=list(LXC_ANSIBLE_STATES.keys()),
                 default='started'
             ),
             container_command=dict(
@@ -1733,7 +1733,7 @@ def main():
                 type='path',
             ),
             archive_compression=dict(
-                choices=LXC_COMPRESSION_MAP.keys(),
+                choices=list(LXC_COMPRESSION_MAP.keys()),
                 default='gzip'
             )
         ),