Will not use Transaction when call db/insert with a binding to *db-connection*

[jiegao1977]

@camsaul
We found when call db/transaction with a binding db-connection, it will never work, since the
connection function will always return db-connection. What I suggest is to adjust the priority to move transaction-connection to the top. I do some testing in my local env, it works.
(defn connection []
(or transaction-connection ;;fix the bug move transaction to the top, otherwise transaction will not work.
db-connection
@default-db-connection
(throw (Exception. "DB is not set up. Make sure to call set-default-db-connection! or bind db-connection.")))))))