Support multi local chrony servers

In the old implementation, if there is no external ntp server, only one
local chrony server is supported. If multi chrony-server is configured,
chrony client can not sync with them.

In the new implementation
* use VIP to connect chrony-server, which ensure multi local chrony
  servers are supported.
* chrony servers depend on VIP. So chrony-server group should be
  the same with haproxy group.
* prevent chrony client sync from itself.
* Change owner to chrony:kolla for chrony log folder
* fix keysfile path
* use chrony user for centos and ubuntu image
* fix permission issue for /var/lib/chrony folder

Closes-Bug: #1705200
Change-Id: I6e85fda9824b5ddc7a96895425c5932a3566c27e