Refresh checked state when choosing certificates.

Change-Id: Icba8e75deaec1ffed7f11378cd2fe77bac40797b
Fix: 27913435
diff --git a/src/com/android/keychain/KeyChainActivity.java b/src/com/android/keychain/KeyChainActivity.java
index 9125203..b5058b2 100644
--- a/src/com/android/keychain/KeyChainActivity.java
+++ b/src/com/android/keychain/KeyChainActivity.java
@@ -213,6 +213,7 @@
         final ListView lv = (ListView) View.inflate(this, R.layout.cert_chooser, null);
         lv.addHeaderView(contextView, null, false);
         lv.addFooterView(footer, null, false);
+        lv.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
         lv.setAdapter(adapter);
         builder.setView(lv);
 
@@ -220,6 +221,7 @@
 
                 public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                     lv.setItemChecked(position, true);
+                    adapter.notifyDataSetChanged();
                 }
         });