correct IAM token service endpoint

[hdaur]

IAM provides a global endpoint for token service. This should be used
https://iam.cloud.ibm.com/identity/token
old us south: https://iam.ng.bluemix.net/oidc/token
old-global: https://iam.bluemix.net/oidc/token

old urls will continue to work for 'some' time, but in any case we should use the global url.

[bruceadams]

It looks like this has been fixed throughout (meaning this issue can be closed).

$ git grep iam
runtimes/nodejs/actions/bucket-cors-delete.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/nodejs/actions/bucket-cors-get.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/nodejs/actions/bucket-cors-put.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/nodejs/actions/object-delete.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/nodejs/actions/object-read.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/nodejs/actions/object-write.js:  const ibmAuthEndpoint = args.ibmAuthEndpoint || 'https://iam.cloud.ibm.com/identity/token';
runtimes/python/actions/bucket-cors-delete.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/bucket-cors-get.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/bucket-cors-put.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/client-get-signed-url.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/object-delete.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/object-read.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')
runtimes/python/actions/object-write.py:  ibm_auth_endpoint = args.get('ibmAuthEndpoint', 'https://iam.cloud.ibm.com/identity/token')