updating dir mode on every run. 

This update makes it more idempotent.

server_source line 146)
       [2014-11-06T21:38:43+00:00] INFO: directory[/var/log/nagios] mode changed to 755
           - change mode from '0751' to '0755'
           - restore selinux security context
         * directory[/var/log/nagios] action create
.......
default line 205)
       [2014-11-06T21:38:43+00:00] INFO: directory[/var/log/nagios] mode changed to 751
           - change mode from '0755' to '0751'
           - restore selinux security context
         * directory[/var/log/nagios/rw] action create