service rollback: always verify state
service rollback: always verify state

Prior to this change, progressbars would sometimes be hidden, and the function
would return early. In addition, the direction of the progressbars would sometimes
be "incrementing" (similar to "docker service update"), and sometimes be "decrementing"
(to indicate a "rollback" is being performed).

This fix makes sure that we always proceed with the "verifying" step, and now
prints a message _after_ the verifying stage was completed;

    $ docker service rollback foo
    foo
    overall progress: rolling back update: 5 out of 5 tasks
    1/5: running   [>                                                  ]
    2/5: starting  [===========>                                       ]
    3/5: starting  [===========>                                       ]
    4/5: running   [>                                                  ]
    5/5: running   [>                                                  ]
    verify: Service converged
    rollback: rollback completed

    $ docker service rollback foo
    foo
    overall progress: rolling back update: 1 out of 1 tasks
    1/1: running   [>                                                  ]
    verify: Service converged
    rollback: rollback completed

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>

cpuguy83/cli,docker/cli,docker/cli,cpuguy83/cli,thaJeztah/cli,thaJeztah/cli