Move race-condition fix to a separate branch

Author: aseering

google/cloud/spanner_v1/snapshot.py

@@ -638,10 +638,6 @@ def _get_streamed_result_set(
         if self._transaction_id is None:
             is_inline_begin = True
             self._lock.acquire()
-            if self._transaction_id is not None:
-                is_inline_begin = False
-                self._lock.release()
-                request.transaction = TransactionSelector(id=self._transaction_id)
 
         iterator = _restart_on_unavailable(
             method=method,

google/cloud/spanner_v1/transaction.py

@@ -512,9 +512,6 @@ def execute_update(
         if self._transaction_id is None:
             is_inline_begin = True
             self._lock.acquire()
-            if self._transaction_id is not None:
-                is_inline_begin = False
-                self._lock.release()
 
         execute_sql_request = ExecuteSqlRequest(
             session=session.name,
@@ -673,9 +670,6 @@ def batch_update(
         if self._transaction_id is None:
             is_inline_begin = True
             self._lock.acquire()
-            if self._transaction_id is not None:
-                is_inline_begin = False
-                self._lock.release()
 
         execute_batch_dml_request = ExecuteBatchDmlRequest(
             session=session.name,