css: do not outline forms with focus

public/css/module.less

@@ -7,6 +7,10 @@ div.action-bar a:focus, .tabs a:focus {
   }
 }
 
+form:focus {
+  outline: none;
+}
+
 div.action-bar a, div.action-bar form i {
   color: @icinga-blue;
 }