Add tests to verify sealing memfds with the F_SEAL_FUTURE_WRITE works as expected. Cc: dancol@google.com Cc: minchan@kernel.org Cc: Jann Horn <jannh@google.com> Cc: John Stultz <john.stultz@linaro.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Reviewed-by: Shuah Khan <shuah@kernel.org> Change-Id: I42a0ceb1f584a5444ec755f8c76899499bcbaddd