Modify check_bucket method from AWSServerAccess

[EduLeon12]

Related issue
Closes #15016

Description

AWSServerAccess integration was not processing logs found in the root folder of the bucket unless it had folders inside of it.
Bug and Fix is described here:

• AWS Server Access check_bucket bug #15016

Fix consist in evaluating existence of "Contents" list after getting Bucket Objects.

Logs/Alerts example

Until now, when trying to get server access S3 bucket objects without a folder existing in the root folder, this error would appear:

/var/ossec/wodles/aws/aws-s3 -b wazuh-aws-wodle-access -t server_access -s 2021-NOV-12 -p dev -d2
DEBUG: +++ Debug mode on - Level: 2
ERROR: No files were found in 'wazuh-aws-wodle-access/'. No logs will be processed.

Now logs are found when there are no folders in root of Bucket as seen on image,

root@wazuh-master:/var/ossec/wodles/aws# /var/ossec/wodles/aws/aws-s3 -b wazuh-aws-wodle-access-test -t server_access -s 2021-APR-29 -p dev -d2
DEBUG: +++ Debug mode on - Level: 2
DEBUG: +++ Marker: 2021-04-29
DEBUG: ++ Found new log: 2021-04-29-09-13-06-338835093EADA3C1
DEBUG: ++ Found new log: 2021-04-29-09-14-05-B61AAAC9147C7F9F
DEBUG: ++ Skipping previously processed file: 2021-04-29-09-14-48-5273CCCAE2158DCE
DEBUG: +++ DB Maintenance

S3 Bucket Image:

Tests

=============================================== test session starts ===============================================
platform linux -- Python 3.10.6, pytest-7.2.1, pluggy-1.0.0
rootdir: /home/halothus/git/wazuh/wodles/aws
collected 39 items                                                                                                

tests/test_aws.py .......................................                                                   [100%]

=============================================== 39 passed in 0.16s ================================================

[nico-stefani]

LGTM