seccomp: add shmctl(), mlock(), and munlock() to the syscall whitelist

Additional testing reveals that PulseAudio requires shmctl() and the
mlock()/munlock() syscalls on some systems/configurations.  As before,
on systems that do require these syscalls, the problem can be seen with
the following command line:

  # qemu -monitor stdio  -sandbox on \
         -device intel-hda -device hda-duplex

Signed-off-by: Paul Moore <pmoore@redhat.com>
Acked-by: Eduardo Otubo <otubo@linux.vnet.ibm.com>