AWS role switch to call Rally's APIs for Performance Testing

[owaiskazi19]

Is your feature request related to a problem? Please describe.
To use rally with the whitelisted account the current aws role in jenkins needs to be set off and the whitelisted role should be activated to call Rally's APIs.

Describe the solution you'd like
Use the plugin: https://github.com/aws-samples/cdk-assume-role-credential-plugin

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Related to: #215