Rsyslog doesn't have write permission to /var/log/mysql/ directory

Detailed bug description:
In Mirantis OpenStack 9.0 Rsyslog does not have write permission to /var/log/mysql/ directory. User 'syslog' belongs to 'adm' group, but /var/log/mysql/ directory has only r.x attributes for this group.
Therefore Rsyslog cannot create MySQL log files.
This bug appeared in the process of solving next bug: https://bugs.launchpad.net/fuel/+bug/1550984

Steps to reproduce:
 Check existence of MySQL log file /var/log/mysql/mysqld.log

Expected results:
  MySQL logs should be in log file /var/log/mysql/mysqld.log

Actual result:
  Log file /var/log/mysql/mysqld.log does not exist

Reproducibility:
  Reproduced on several MOS 9 environments

Workaround:
  # chmod 770 /var/log/mysql/

Impact:
  Currently we don’t have any MySQL logs in all deployments (apart from the error.log because it was created at the time of deployment and does not contain any useful info).
  This is critical bug because it makes difficult to analyze MySQL issues.
  This bug also found on customer environment

Description of the environment:
 Operation system: Ubuntu 14.04
 Versions of components: MOS 9.0

Additional information:

----------------------
[root@fuel ~]# cat /etc/fuel_build_id
495
[root@fuel ~]# cat /etc/fuel_release
9.0
[root@fuel ~]# cat /etc/fuel_openstack_version
mitaka-9.0

----------------------
root@node-1:~# id syslog
uid=101(syslog) gid=104(syslog) groups=104(syslog),4(adm)

----------------------
root@node-1:~# ll /var/log/mysql/
total 16
drwxr-x--- 2 mysql adm 4096 Aug 22 11:50 ./
drwxrwxr-x 27 root syslog 4096 Aug 22 10:49 ../
-rw-r----- 1 mysql adm 6758 Aug 20 20:06 error.log

----------------------
root@node-1:~# cat /etc/rsyslog.d/04-mysql.conf
# This file is managed by Puppet, changes may be overwritten
# managed by puppet

### collect mysql* logs of all levels in /var/log/mysqld.log
if ($programname == 'mysql' \
  or $programname == 'mysqld' \
  or $programname == 'mysqld_safe' \
  or $programname == 'mysql_slow' \
  or $programname == 'mysql-wss') \
then -/var/log/mysql/mysqld.log
### stop further processing for the matched entries
& ~

----------------------
Rsyslog debug info:
0835.920442032:7f46461f2700: entering actionCalldoAction(), state: itx
0835.920443874:7f46461f2700: file to log to: /var/log/mysql/mysqld.log
0835.920445619:7f46461f2700: omfile: start of data: '<30>Aug 22 13:00:35 node-1 ocf-mysql-wss: INFO: p_mysqld: check_if_sst(): MySQL process 532597 found'
0835.920447393:7f46461f2700: write to stream, pData->pStrm 0x7f46400149e0, lenBuf 101
0835.920449600:7f46461f2700: action 0x2385880 call returned -2121
0835.920452931:7f46461f2700: strm 0x7f46400149e0: file -1(mysqld.log) flush, buflen 101
0835.920458135:7f46461f2700: strmPhysWrite, stream 0x7f46400149e0, len 101
0835.920467866:7f46461f2700: file '/var/log/mysql/mysqld.log' opened as #-1 with mode 416
0835.920472950:7f46461f2700: strm 0x7f46400149e0: open error 13, file '/var/log/mysql/mysqld.log': Permission denied