Plugin does not work with codebuild ec2 container service iam metadata

[jeugene]

Plugin does not work with ec2 container service that exposes AWS_CONTAINER_CREDENTIALS_RELATIVE_URI instead of metadata

Credentials delivered through the Amazon EC2 container service if AWS_CONTAINER_CREDENTIALS_RELATIVE_URI" environment variable is set and security manager has permission to access the variable
#4 https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/auth/DefaultAWSCredentialsProviderChain.html