test/nptl/tst-mqueue4.c: fix build with latest glibc

Fix the following error with latest glibc:

In file included from /home/fabrice/buildroot/output/host/riscv32-buildroot-linux-gnu/sysroot/usr/include/mqueue.h:93:0,
                 from tst-mqueue4.c:22:
In function 'mq_open',
    inlined from 'do_test' at tst-mqueue4.c:174:6:
/home/fabrice/buildroot/output/host/riscv32-buildroot-linux-gnu/sysroot/usr/include/bits/mqueue2.h:41:5: error: call to '__mq_open_wrong_number_of_args' declared with attribute error: mq_open can be called either with 2 or 4 arguments
     __mq_open_wrong_number_of_args ();
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Fixes:
 - http://autobuild.buildroot.net/results/f370abcc8dc12975d96a46c34db978554f8c21db

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>

test/nptl/tst-mqueue4.c

@@ -171,14 +171,14 @@ do_test (void)
       result = 1;
     }
 
-  q2 = mq_open (name, O_RDONLY, 0600);
+  q2 = mq_open (name, O_RDONLY, 0600, &attr);
   if (q2 == (mqd_t) -1)
     {
       printf ("mq_open without O_CREAT failed with %m\n");
       result = 1;
     }
 
-  mqd_t q3 = mq_open (name, O_RDONLY, 0600);
+  mqd_t q3 = mq_open (name, O_RDONLY, 0600, &attr);
   if (q3 == (mqd_t) -1)
     {
       printf ("mq_open without O_CREAT failed with %m\n");