Merge with master

drop py2 support

on-behalf-of: @StackStorm-Exchange <[email protected]>

Update pack/change log

Updated pack and changes file

Add group actions

Update changelog and bump pack version to 0.7.3

Update OpenStack environment variables

The origin environment variables are quite outdated now.
Let's update these to Keystone version 3 compatible.

Version bump to fix tagging issue

Add neutron and aodh alarm related yaml configurations

Use autogen script to generate neutron and aodh alarm related yaml
configurations. Besides, add aodhclient to requirements.

Remove deprecated st2actions import