Fix logging in ExtServices for Q Beta

Two issues:
1. The notification key -> logging id mapping should be removed
   whenever suggest() is called as the session is considered to be ended.

2. We were only storing the key -> logging id mapping when
   suggestConversationActions generated some replies. Thus, when only smart actions
   are generated from generateLinks, we didn't log it (as the mapping is missing)
   So, we now always cache the ID after calling suggestConversationActions.
   Remove the mapping when we find that neither actions or replies
   are generated.
   PS: We have a CL (ag/6033786) to switch to suggestConversationActions,
   fix for #2 is no longer needed once it is in. But that change won't
   be in before Android Beta as the model side change is not done.

BUG: 120803809
Test: Manual. Send a message with URL, observer subsequent events (e.g:
clicked) are logged.
Test: atest SmartActionHelperTest

Change-Id: Iea1a46466846ef99d51316dcbb294bfe0cf33653