Fix Conpherence durable scrollbar with no USB devices

Summary:
Ref T7014.

When no devices are connected, we don't meaningfully activate `JX.Scrollbar` (by design), but there was no fallback overflow CSS.

Also massage a couple of other CSS things to get sliiightly less broken behavior.

Test Plan:
  - Disconnected USB devices; scrolled.
  - Connected USB devices; scrolled.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T7014

Differential Revision: https://secure.phabricator.com/D12008

resources/celerity/map.php

@@ -44,7 +44,7 @@ return array(
     'rsrc/css/application/config/config-welcome.css' => '6abd79be',
     'rsrc/css/application/config/setup-issue.css' => '22270af2',
     'rsrc/css/application/config/unhandled-exception.css' => '37d4f9a2',
-    'rsrc/css/application/conpherence/durable-column.css' => '3b836442',
+    'rsrc/css/application/conpherence/durable-column.css' => '1ef6ae75',
     'rsrc/css/application/conpherence/menu.css' => 'c6ac5299',
     'rsrc/css/application/conpherence/message-pane.css' => '5930260a',
     'rsrc/css/application/conpherence/notification.css' => '04a6e10a',
@@ -512,7 +512,7 @@ return array(
     'changeset-view-manager' => 'fce415a0',
     'config-options-css' => '7fedf08b',
     'config-welcome-css' => '6abd79be',
-    'conpherence-durable-column-view' => '3b836442',
+    'conpherence-durable-column-view' => '1ef6ae75',
     'conpherence-menu-css' => 'c6ac5299',
     'conpherence-message-pane-css' => '5930260a',
     'conpherence-notification-css' => '04a6e10a',