Handles transactions started immediately after completion

Unset mIsTransactionPending before invoking handleTxnResult
to allow service to start a new transaction.

Bug: 70387233
Test: Run a sample application that concurrently loads and unloads 2
nanoapps, verify both transactions succeed.

Change-Id: I465882dd8fd8fdd89b959642f6fdc2e452ce61a6

contexthub/1.0/default/Contexthub.cpp

@@ -281,11 +281,11 @@ int Contexthub::handleOsMessage(sp<IContexthubCallback> cb,
                 result = TransactionResult::FAILURE;
             }
 
+            mIsTransactionPending = false;
             if (cb != nullptr) {
                 cb->handleTxnResult(mTransactionId, result);
             }
             retVal = 0;
-            mIsTransactionPending = false;
             break;
         }