add dhcp_checker package on centos node
Add /dump alias for Nginx to retrive logs from /var/www/nailgun/dump
Merge pull request #577 from e0ne/nailgun-logs-dump

Add /dump alias for Nginx to retrive logs from /var/www/nailgun/dump
Merge pull request #573 from dshulyak/feature/dhcp_checker_on_centos

add dhcp_checker package on centos node
Merge remote-tracking branch 'origin/master' into ubuntu-3.2-WIP