Provide option to update SSH credentials stored in Fabric without showing password in clear

When SSH credentials change, customer's are required to update the SSH credentials stored in fabric which are used by commands such as fabric:container-start, fabric:container-stop, and fabric:container-delete.

The credentials are originally stored when the SSH container is created, and this can be done via Hawtio which will hide the password on the screen, however when the credentials change they have to be updated on the command line by passing them as an argument to a command like fabric:container-stop and the password is shown in the clear on the screen. This violates some customer's security policies.