score: don't mask signals if we fail to setup signal stack

If setup_rt_frame() returns -EFAULT then we must not block any signals
in the current process.

Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chen Liqin <liqin.chen@sunplusct.com>
Cc: Lennox Wu <lennox.wu@gmail.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>