Integration tests - add option to change number of log lines

[Daniel Korn]

The option to change the number of log lines to be shown per instance was added to the settings page.
Therefore, the same option should be added to the integration tests's page and change user settings test.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/158114

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/158114
Committed: https://git.openstack.org/cgit/openstack/horizon/commit/?id=2344ac739f973292bd03937204920837f55e974e
Submitter: Jenkins
Branch: master

commit 2344ac739f973292bd03937204920837f55e974e
Author: dkorn <email address hidden>
Date: Sun Feb 22 11:04:07 2015 +0200

    Add log lines change to settings page and test

    I added the option to change the number of log lines to be shown per
    instance to settings page and updated test_user_settings.py to verify
    it works.

    Partially implements blueprint: selenium-integration-testing
    Closes-Bug #1424344

    Change-Id: I22bf13ace46398078f5a58321e3106bf56fa2701