selftests/damon: Add executable permission to test scripts

When running the test for the damon subsystem, there are a lot of
warnings because test scripts do not have executable permission,
for example:

Warning: file debugfs_attrs.sh is not executable
Warning: file debugfs_schemes.sh is not executable
Warning: file debugfs_target_ids.sh is not executable
...

This patch adds executable permission to test scripts to eliminate
these warnings.

Signed-off-by: Juntong Deng <juntong.deng@outlook.com>
Reviewed-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

selftests/damon/debugfs_rm_non_contexts: hide expected write error messages

A selftest case for DAMON debugfs interface has a test for expected
failure. To make the test output clean, hide the expected failure error
message.

Link: https://lkml.kernel.org/r/20230110190400.119388-9-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

selftests/damon: test non-context inputs to rm_contexts file

There was a bug[1] that triggered by writing non-context DAMON debugfs
file names to the 'rm_contexts' DAMON debugfs file. Add a selftest for
the bug to avoid it happen again.

[1] https://lore.kernel.org/damon/000000000000ede3ac05ec4abf8e@google.com/

Link: https://lkml.kernel.org/r/20221107165001.5717-3-sj@kernel.org
Signed-off-by: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>