fix(cleftbar): leftbar can't scroll

when get long host list, leftbar can't scroll

#1012

src/app/ControlPage/cleftbar/cleftbar.component.css

@@ -78,3 +78,10 @@ label {
 .fa.fa-undefined:before {
   content: "\f26c";
 }
+
+.overflow {
+  height: 100%;
+  overflow-y: scroll;
+  position: absolute;
+  width: 100%;
+}

src/app/ControlPage/cleftbar/cleftbar.component.html

@@ -4,19 +4,23 @@
            title="Search"
            type="text" tabindex="1" spellcheck="false" autofocus [(ngModel)]="q" (keyup.enter)="Search(q)">
   </div>
+  <div class="overflow">
     <ul class="filetree">
       <li *ngFor="let hostGroup of HostGroups | SearchFilter: q; let i = index ">
         <input type="checkbox" id="hostgroup-{{i}}">
         <label for="hostgroup-{{i}}" matTooltip="{{hostGroup.name}}" [matTooltipPosition]="TooltipPosition">{{hostGroup.name}}</label>
         <ul [ngClass]="{'insearch': q }">
           <li *ngFor="let host of hostGroup.assets_granted | SearchFilter: q" (click)="Connect(host)"
-            (contextmenu)="onRightClick($event)" matTooltip="{{host.hostname}}" [matTooltipPosition]="TooltipPosition">
+              (contextmenu)="onRightClick($event)" matTooltip="{{host.hostname}}"
+              [matTooltipPosition]="TooltipPosition">
             <i class="fa" [ngClass]="'fa-'+(host.platform||'undefined').toLowerCase()" id="fa-{{i}}"></i>
             {{host.hostname}}
           </li>
         </ul>
       </li>
     </ul>
+  </div>
+
 </div>
 <div class="footer">
   Version <strong>{{version}}</strong>