fix: initialize transactionMu in NewAdapterByDBUseTableName

constructor NewAdapterByDBUseTableName should initialize transactionMu,
otherwise it will ~~panic~~ blocked due to that cas when calling Transaction

Besides, a few other constructors also depend on NewAdapterByDBUseTableName,
if transactionMu is not initialized in NewAdapterByDBUseTableName,
it will blocked as well.

adapter.go

@@ -200,8 +200,9 @@ func NewAdapterByDBUseTableName(db *gorm.DB, prefix string, tableName string) (*
 	}
 
 	a := &Adapter{
-		tablePrefix: prefix,
-		tableName:   tableName,
+		tablePrefix:   prefix,
+		tableName:     tableName,
+		transactionMu: &sync.Mutex{},
 	}
 
 	a.db = db.Scopes(a.casbinRuleTable()).Session(&gorm.Session{Context: db.Statement.Context})