Aws-parallelcluster

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- Refactor scaling up to take into account the number of pending/requested jobs/slots and instance slots.
- Refactor scaling down to scale down faster and take advantage of per-second billing.
- Add ``scaledown_idletime`` parameter as part of scale-down refactoring
- Lock hosts before termination to ensure removal of dead compute nodes from host list
- Fix HTTP proxy support

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- Add option to disable ganglia ``extra_json = { "cfncluster" : { "ganglia_enabled" : "no" } }``
- Fix ``cfncluster update``bug
- Set SGE Accounting summary to be true, this reports a single accounting record for a mpi job
- Upgrade cfncluster-node to Boto3

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- Add support for GovCloud, us-gov-west-1 region

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- feature:``cfncluster``: Added ClusterUser as a stack output. This makes it easier to get the username of the head node.
- feature:``cfncluster``: Added ``cfncluster ssh cluster_name``, this allows you to easily ssh into your clusters.
It allows arbitrary command execution and extra ssh flags to be provided after the command.
See https://aws-parallelcluster.readthedocs.io/en/latest/commands.html#ssh
- change:``cfncluster``: Moved global cli flags to the command specific flags.
For example ``cfncluster --region us-east-1 create``now becomes ``cfncluster create --region us-east-1``
- bugfix:``cfncluster-cookbook``: Fix bug that prevented c5d/m5d instances from working
- bugfix:``cfncluster-cookbook``: Set CPU as a consumable resource in slurm
- bugfix:``cfncluster-node``: Fixed Slurm behavior to add CPU slots so multiple jobs can be scheduled on a single node

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- change:``cfncluster``: Added "ec2:DescribeVolumes" permissions to
CfnClusterInstancePolicy
- change:``cfncluster``: Removed YAML CloudFormation template, it can be
generated by the https://github.com/awslabs/aws-cfn-template-flip tool
- updates:``cfncluster``: Add support for eu-west-3 region
- feature:``cfncluster-cookbook``: Added parameter to specify custom
cfncluster-node package
- bugfix:``cfncluster``: Fix --template-url command line parameter
- bugfix:``cfncluster-cookbook``: Poll on EBS Volume attachment status
- bugfix:``cfncluster-cookbook``: Fixed SLURM cron job to publish pending metric
- bugfix:``cfncluster-node``: Fixed Torque behaviour when scaling up from an empty cluster

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- bugfix:``cfncluster``: Fix crash when base directory for config file
does not exist
- bugfix:``cfncluster``: Removed extraneous logging message at
cfncluster invocation, re-enabled logging in ~/.cfncluster/cfncluster-cli.log
- bugfix: ``cfncluster-node``: Fix scaling issues with CentOS 6 clusters caused
by incompatible dependencies.
- updates:``ami``: Update all base AMIs to latest patch levels
- updates:``cfncluster-cookbook``: Updated to cfncluster-cookbook-1.4.1