ELB enhancements

* connection draining
* cross AZ load balancing
The correct option is password_file. Fixes #8752
Merge branch 'elb-enhancements' of https://github.com/dataxu/ansible into dataxu-elb-enhancements
Add boto support checks for new ec2_elb_lb attribute fields

Also minor fixes like adjusting version_added fields, etc.
Merge branch 'dataxu-elb-enhancements' into devel
Merge pull request #8757 from sivel/issue/8752

ansible-vault: The correct option is password_file. Fixes #8752