Sets clickability of QuickStatusBarHeader

Sets the clickability based on QS expansion. Then, when it's expanded,
it is not clickable as QSPanel captures clicks. The top status bar is
always clickable

Test: manual, including brightness slider
Change-Id: Id41473f823285f115240effbea7a2d52596b9bfe
Fixes: 120873445

packages/SystemUI/res/layout/quick_status_bar_header_system_icons.xml

@@ -24,6 +24,7 @@
     android:clipToPadding="false"
     android:gravity="center"
     android:orientation="horizontal"
+    android:clickable="true"
     android:paddingStart="@dimen/status_bar_padding_start"
     android:paddingEnd="@dimen/status_bar_padding_end" >
 

packages/SystemUI/src/com/android/systemui/qs/QuickStatusBarHeader.java

@@ -699,7 +699,7 @@ public class QuickStatusBarHeader extends RelativeLayout implements
     }
 
     public void updateEverything() {
-        post(() -> setClickable(false));
+        post(() -> setClickable(!mExpanded));
     }
 
     public void setQSPanel(final QSPanel qsPanel) {