[ui] Custom checkboxes don't support indeterminate state

[Julia Aranovich]

Since we moved to custom checkboxes in Assign Roles panel we lost support of indeterminate checkboxes state.

There is no custom picture for indeterminate custom checkboxes.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/144099

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/144099
Committed: https://git.openstack.org/cgit/stackforge/fuel-web/commit/?id=4990d684a11c4eb117e4c8644357052466a5104b
Submitter: Jenkins
Branch: master

commit 4990d684a11c4eb117e4c8644357052466a5104b
Author: Julia Aranovich <email address hidden>
Date: Thu Dec 25 18:50:35 2014 +0300

    Fixes custom checkboxes indeterminate state

    Closes-Bug: #1405641

    Change-Id: Ifa75d8adbb1f8322bb5b7f793bffa2acabbc8e13

[Anastasia Palkina (apalkina)]

Verified on ISO #58

"build_id": "2015-01-13_21-50-03", "ostf_sha": "0c1b663c6fc02ad972f2ed9ff6b000e7be1ea207", "build_number": "58", "auth_required": true, "api": "1.0", "nailgun_sha": "6fa6147384b533fb3d56cdc49ec6ecbcca47675d", "production": "docker", "fuelmain_sha": "", "astute_sha": "82125b0eef4e5a758fd4afa8917812e09a1f7dac", "feature_groups": ["mirantis"], "release": "6.1", "release_versions": {"2014.2-6.0": {"VERSION": {"build_id": "2015-01-13_21-50-03", "ostf_sha": "0c1b663c6fc02ad972f2ed9ff6b000e7be1ea207", "build_number": "58", "api": "1.0", "nailgun_sha": "6fa6147384b533fb3d56cdc49ec6ecbcca47675d", "production": "docker", "fuelmain_sha": "", "astute_sha": "82125b0eef4e5a758fd4afa8917812e09a1f7dac", "feature_groups": ["mirantis"], "release": "6.1", "fuellib_sha": "c53cb3a2bd5f99f32f78ed18e9472724fa6a9a9e"}}}, "fuellib_sha": "c53cb3a2bd5f99f32f78ed18e9472724fa6a9a9e"