Keep deleteIntent when copying Notification attributes

Ensures that any previously registered deleteIntent is retained after a call
to Notification.setLatestEventInfo().

Currently, a call to setLatestEventInfo() effectively erases a previously
registered Notification.deleteIntent, which results in the app never being
notified when the user dismisses the notification.

This issue is described in detail in #73720:
https://code.google.com/p/android/issues/detail?id=73720

Change-Id: Ie58bf6a310058d40beb0d1af6506e9e1f4324b37
Signed-off-by: Sean Barbeau <sjbarbeau@gmail.com>