fix gingerbread press reaction

Fixes #3392
Closes #3493
// FREEBIE

res/drawable/conversation_list_item_background.xml

@@ -1,4 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <selector xmlns:android="http://schemas.android.com/apk/res/android">
     <item android:drawable="@color/textsecure_primary_alpha33" android:state_selected="true" />
+    <item android:drawable="@color/textsecure_primary_alpha33" android:state_pressed="true" />
 </selector>