selftests/seccomp: Abort without user notification support

In the face of missing user notification support, the self test needs
to stop executing a test (ASSERT_*) instead of just reporting and
continuing (EXPECT_*). This adjusts the user notification tests to do
that where needed.

Reported-by: Shuah Khan <shuah@kernel.org>
Fixes: 6a21cc50 ("seccomp: add a return code to trap to userspace")
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Tycho Andersen <tycho@tycho.ws>
Tested-by: Shuah Khan <shuah@kernel.org>
Signed-off-by: Shuah Khan <shuah@kernel.org>