Call local finish(String) on cancel

Change I439592b2236261fa683484cd5c3ba26795aece47 to honor "Cancel"
button presses caused a call directly into finish() instead of the local
finish(String) which does some extra administrivia.

(cherry picked from commit 13e867cb8d4f45f4a7c7a1552d89dfc5ec95f159)

Bug: 18381187
Bug: https://code.google.com/p/android/issues/detail?id=79208
Change-Id: Ica7f52ce3afa82d95ea5cc3cb15c9ac7b734cf93
diff --git a/src/com/android/keychain/KeyChainActivity.java b/src/com/android/keychain/KeyChainActivity.java
index 3859f05..23aa1a1 100644
--- a/src/com/android/keychain/KeyChainActivity.java
+++ b/src/com/android/keychain/KeyChainActivity.java
@@ -127,7 +127,7 @@
             case UNLOCK_CANCELED:
                 // User wanted to cancel the request, so exit.
                 mState = State.INITIAL;
-                finish();
+                finish(null);
                 return;
             default:
                 throw new AssertionError();