fix V2 auth timestamp

Amazon describes common header parameters here -
http://docs.aws.amazon.com/AWSEC2/latest/APIReference/Query-Common-Parameters.html
Timestamp should be in ISO8601 format. But datetime.isoformat() generates
string in format that not compatible with ISO8601.
I prefer to copy this from requestbuilder that used by euca2ools.
Merge branch 'release-0.52.0' into develop

* release-0.52.0:
  Bumping version to 0.52.0
  Upate JSON models to latest version
  Update dynamodb port to be port 8000
add test for #308
Fix region endpoint for cn-north-1

The endpoint heuristic rule is wrong.
Also looks like the local region changes
weren't scripts/buildall'd, so that shows
up in the diff
Merge branch 'fix-endpoints' into develop

* fix-endpoints:
  Fix region endpoint for cn-north-1
Fix regression in EC2 credential provider parsing

The only parser basically had::

    config = dict(line.split('=', 1) for line in lines if '=' in line)
    access_key = config.get('AWSAccessKeyId')
    secret_key = config.get('AWSSecretKey')

Which ignores lines that don't have a '=' char in it.
This behavior has been re-added and additional tests to cover a few of
these edge cases have also been added.
Merge branch 'ec2-cred-provider' into develop

* ec2-cred-provider:
  Fix regression in EC2 credential provider parsing
Merge branch 'Andrey-mp-develop' into develop

* Andrey-mp-develop:
  add test for #308
  fix V2 auth timestamp
Update SES model to the latest version
Bumping version to 0.53.0
Merge branch 'release-0.53.0'

* release-0.53.0:
  Bumping version to 0.53.0
  Update SES model to the latest version
  Fix regression in EC2 credential provider parsing
  Fix region endpoint for cn-north-1
  add test for #308
  fix V2 auth timestamp