tools/testing/selftests/mm/run_vmtests.sh: lower the ptrace permissions

On Ubuntu and probably other distros, ptrace permissions are tightend a
bit by default; i.e., /proc/sys/kernel/yama/ptrace_score is set to 1. 
This cases memfd_secret's ptrace attach test fails with a permission
error.  Set it to 0 piror to running the program.  

Link: https://lkml.kernel.org/r/20231030-selftest-v1-1-743df68bb996@linux.dev
Signed-off-by: Itaru Kitayama <itaru.kitayama@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: Itaru Kitayama

tools/testing/selftests/mm/run_vmtests.sh

@@ -303,6 +303,7 @@ CATEGORY="hmm" run_test bash ./test_hmm.sh smoke
 # MADV_POPULATE_READ and MADV_POPULATE_WRITE tests
 CATEGORY="madv_populate" run_test ./madv_populate
 
+echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
 CATEGORY="memfd_secret" run_test ./memfd_secret
 
 # KSM KSM_MERGE_TIME_HUGE_PAGES test with size of 100