Fix security group modal header overflow

If you go to Edit Instance > Security Group
The two headers "All Security Groups" and "Instance Security Groups"
overflow when translated

Change-Id: I5acd0e4670a6595e6f38ba7f17371b6329ed5836
Closes-Bug:#1288402
(cherry picked from commit 0048dfc)

openstack_dashboard/static/dashboard/less/horizon.less

@@ -1656,6 +1656,7 @@ label.log-length {
     font-weight: bold;
     padding-left: 10px;
     float: left;
+    width: 160px;
   }
   input {
     background: url(/static/dashboard/img/search.png) no-repeat 105px 5px whiteSmoke;