Investigate the invalid creation of transaction manager

[cppwfs]

Based on the following comment: #769 (comment), a transaction manager is still being created eventhough the spring.cloud.task.transaction-manager is being used.

Investigate.

[loki-y-chen]

I have set the following property:

spring.cloud.task.transaction-manager=transactionManager

This allows the transactionManager created by DataSourceTransactionManagerAutoConfiguration to work correctly.

However, when I add the following additional setting:

spring.cloud.task.transaction-manager=transactionManager
spring.cloud.task.single-instance-enable=true

It breaks because it cannot find a bean named springCloudTaskTransactionManager.