ec2_facts: add ansible_ec2_placement_region key/value pair for EC2 region.
copy action plug-in check mode respects force=no

The copy action accepts force=no, which tells it not to replace an
existing file even if it differs from the source.  The copy action
plug-in wasn't respecting this option when operated in check mode, so it
would report that changes are necessary in check mode even though copy
would make no changes when run normally.

Runner._remote_md5 was changed to make the logic for setting rc perhaps
a little more clear, and to make sure that rc=0 when the file does not
exist.
Merge pull request #2596 from blair/ec2_facts-provides-ec2-region

ec2_facts: add ansible_ec2_placement_region key/value pair for EC2 regio...
Fix with_sequence doc error