Update the Concourse "aggregate" step to "in_parallel"

[nvpnathan]

https://concourse-ci.org/aggregate-step.html

DEPRECATION WARNING:

• jobs.install-nsx-t.plan[0] : aggregate is deprecated and will be removed in a future version
• jobs.add-nsx-t-routers.plan[0] : aggregate is deprecated and will be removed in a future version
• jobs.config-nsx-t-extras.plan[0] : aggregate is deprecated and will be removed in a future version
• jobs.standalone-install-nsx-t.plan[0] : aggregate is deprecated and will be removed in a future version
• jobs.standalone-add-nsx-t-routers.plan[0] : aggregate is deprecated and will be removed in a future version
• jobs.standalone-config-nsx-t-extras.plan[0] : aggregate is deprecated and will be removed in a future version