username's length is not limit

[tinytmy]

when create a user,we can input length more 255 character,but it will report a error 'User name should not be greater than 255 characters (HTTP 400)'.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/80195

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/80195
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=7de27824e5c4e243016aa0e97659d0c5ef51e214
Submitter: Jenkins
Branch: master

commit 7de27824e5c4e243016aa0e97659d0c5ef51e214
Author: tinytmy <email address hidden>
Date: Thu Mar 13 00:23:55 2014 -0700

    Fix username's maximum length to match the backend

    when create a user, we can input length more 255 character,
    but it will report a error 'User name should not be greater
    than 255 characters (HTTP 400)'.

    Change-Id: Ib2a3d2f6783e1c107d9a2cf87877442a9171480d
    Closes-bug:#1291216