In case of multiple NSX managers in the nsx_api_managers configuration,
it is now possible to configure a different username/password/ca_file for each
of the managers.
The nsxv3 configuration parameters ca_file, nsx_api_user & nsx_api_password are
now lists.
If they contain only 1 value, it will be used for all the managers.
Else, the order of of the values is expected to match the order of the
nsx_api_managers.
Change-Id: I31b955c9ee449126acde96de48a1887b94c38e29