Trac #18495: Call Element.__init__ directly for RealBall

Instead of calling `super(ComplexBall, self).__init__(parent)`, call
`Element.__init__(self, parent)`, see
http://trac.sagemath.org/ticket/17218#comment:14 .

URL: http://trac.sagemath.org/18495
Reported by: cheuberg
Ticket author(s): Clemens Heuberger
Reviewer(s): Vincent Delecroix

src/sage/rings/real_arb.pyx

@@ -931,7 +931,7 @@ cdef class RealBall(RingElement):
         cdef arf_t  tmpr
         cdef mag_t  tmpm
 
-        super(RealBall, self).__init__(parent)
+        Element.__init__(self, parent)
 
         if mid is None:
             return