Fix charts display in Resource Usage

    Due to an error in a patch, the line 638 of horizon.d3linechart.js
has been commented. The consequence of this is that now charts are not
displayed in the Resource usage panel.

Fixes bug #1266505

Change-Id: Ifc9aa6100efdba6c3efd1ea47638a7934f457913
Merge "Fix charts display in Resource Usage"