Simultaneous use of CentOSVZAdapter will cause IP address conflict

[travula]

CentOSVZAdapter relies on a function called find_available_ip which tries to ping all IP addresses in a subnet and find an IP.
When this adapter is used simultaneously, in the same subnet, there is a high potential of IP address conflicts among multiple containers.

Proposed Solution: find_available_ip should maintain a map of allocated and available IP addresses and act more like a DHCP server.