Add support for wso2.carbon >> ports >> offset

[niveathika]

Purpose

When TransportsConfiguration is not given in the API, this supports setting ports offset through wso2.carbon namespace

  # Carbon Configuration Parameters
wso2.carbon:
    # value to uniquely identify a server
  id: siddhi-runner
    # server name
  name: Siddhi Runner Distribution
    # ports used by this server
  ports:
      # port offset
    offset: 1

Goals

Support port offset in carbon configuration

Approach

As in 45f45d0

Release note

Support port offset under carbon configuration if present

Documentation

N/A

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines? yes
• Ran FindSecurityBugs plugin and verified report? yes
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets? yes