Log first known index with megolm session updates

Move the logging lower to a point where we know the first index.

src/crypto/OlmDevice.js

@@ -1032,6 +1032,11 @@ OlmDevice.prototype.addInboundGroupSession = async function(
                             }
                         }
 
+                        logger.info(
+                            "Storing megolm session " + senderKey + "/" + sessionId +
+                            " with first index " + session.first_known_index(),
+                        );
+
                         const sessionData = {
                             room_id: roomId,
                             session: session.pickle(this._pickleKey),

src/crypto/algorithms/megolm.js

@@ -1323,7 +1323,6 @@ MegolmDecryption.prototype.onRoomKeyEvent = function(event) {
         keysClaimed = event.getKeysClaimed();
     }
 
-    logger.log(`Received and adding key for megolm session ${senderKey}|${sessionId}`);
     return this._olmDevice.addInboundGroupSession(
         content.room_id, senderKey, forwardingKeyChain, sessionId,
         content.session_key, keysClaimed,