fix(spanner): release resources in TransactionManager

google-cloud-spanner/src/main/java/com/google/cloud/spanner/TransactionManagerImpl.java

@@ -80,6 +80,13 @@ public void commit() {
  } catch (SpannerException e2) {
  txnState = TransactionState.COMMIT_FAILED;
  throw e2;
+ } finally {
+ // At this point, if the TransactionState is not ABORTED, then the transaction has reached an
+ // end state.
+ // We can safely call close() to release resources.
+ if (getState() != TransactionState.ABORTED) {
+ close();
+ }
  }
  }
 
@@ -92,6 +99,9 @@ public void rollback() {
  txn.rollback();
  } finally {
  txnState = TransactionState.ROLLED_BACK;
+ // At this point, the TransactionState is ROLLED_BACK which is an end state.
+ // We can safely call close() to release resources.
+ close();
  }
  }