Deny socketcall in seccomp filter on ppc64le.

OpenSSL is using socket() calls (in FIPS mode) when handling ECDSA keys
in privsep child. The socket() syscall is already denied in the seccomp
filter, but in ppc64le kernel, it is implemented using socketcall()
syscall, which is not denied yet (only SYS_SHUTDOWN is allowed) and
therefore fails hard.

Patch from jjelen at redhat.com.

sandbox-seccomp-filter.c

@@ -225,6 +225,7 @@ static const struct sock_filter preauth_insns[] = {
 #endif
 #ifdef __NR_socketcall
 	SC_ALLOW_ARG(__NR_socketcall, 0, SYS_SHUTDOWN),
+	SC_DENY(__NR_ssocketcall, EACCES),
 #endif
 #if defined(__NR_ioctl) && defined(__s390__)
 	/* Allow ioctls for ICA crypto card on s390 */