seccomp: add some basic shared memory syscalls to the whitelist

PulseAudio requires the use of shared memory so add shmget(), shmat(),
and shmdt() to the syscall whitelist.

Reported-by: xuhan@redhat.com
Signed-off-by: Paul Moore <pmoore@redhat.com>

qemu-seccomp.c

@@ -222,7 +222,10 @@ static const struct QemuSeccompSyscall seccomp_whitelist[] = {
     { SCMP_SYS(io_destroy), 241 },
     { SCMP_SYS(arch_prctl), 240 },
     { SCMP_SYS(mkdir), 240 },
-    { SCMP_SYS(fchmod), 240 }
+    { SCMP_SYS(fchmod), 240 },
+    { SCMP_SYS(shmget), 240 },
+    { SCMP_SYS(shmat), 240 },
+    { SCMP_SYS(shmdt), 240 }
 };
 
 int seccomp_start(void)