gh-143637: Fix test_socket.test_sendmsg_reentrant_ancillary_mutation() on Solaris (#144890)

Use socket.SCM_RIGHTS operation.

Author: vstinner

Lib/test/test_socket.py

@@ -2228,11 +2228,11 @@ def test_sendmsg_reentrant_ancillary_mutation(self):
         class Mut:
             def __index__(self):
                 seq.clear()
-                return 0
+                return socket.SCM_RIGHTS
 
         seq = [
-            (socket.SOL_SOCKET, Mut(), b'x'),
-            (socket.SOL_SOCKET, 0, b'x'),
+            (socket.SOL_SOCKET, Mut(), b'xxxx'),
+            (socket.SOL_SOCKET, socket.SCM_RIGHTS, b'xxxx'),
         ]
 
         left, right = socket.socketpair()