ec2_placement was missing from the inventory variables ec2.py was
producing.  Make sure that gets properly included rather than ignored.

If a user has full EC2 access but no RDS access, the user
should still be able to query the EC2 inventory, although
will not obtain any information about any RDS instances.

Move the ec2 cache files from a shared /tmp location to the
user's ansible tmp directory.

* make filtering more comprehensive
* add checks against missing route53 zone exclusion option

names.

listing EC2 inventory

adding regions_exclude parameter to be able to do subtractive region exclusion. Defaults to us-gov-west-1 so as to not cause errors for people who don't have govcloud credentials but get it in their regions list

ec2 inventory: Verify that a security group exists before trying to use its name as a key in inventory.

Only inventory "running" EC2 instances. "stopped" is also a valid state and these should not be inventoried.

without a keypair, so this takes care of that scenario