seccomp: exit if seccomp_init() fails

This fixes a bug where we weren't exiting if seccomp_init() failed.

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

qemu-seccomp.c

@@ -231,6 +231,7 @@ int seccomp_start(void)
 
     ctx = seccomp_init(SCMP_ACT_KILL);
     if (ctx == NULL) {
+        rc = -1;
         goto seccomp_return;
     }