Added ability to set custom acceptance testing node IP addresses
Test for some cases handled by Tom Prince's branch
lint fix
Don't cast to a set twice
Don't just check one node
Set acceptance nodes with env variable in release process
Fixed trial command
Handle the case where the acceptance nodes variable is not set
Updated get_nodes comment to reflect new truth
Better documentation and error string
Get rid of break in loop
Run tests if enough but not all nodes are reachable
Improved error if there are not enough reachable nodes
Merge pull request #1004 from ClusterHQ/configure-acceptance-nodes-FLOC-1033

[FLOC-1033] Allow specifying nodes to use for acceptance testing.

Author: @adamtheturtle
Reviewer: @tomprince