Host affinity improvements - Improve matching of hosts to allocated resources

Kudos to abkshvn for observing this!

We have observed host-affinity not being honored for some containers in very large jobs. When Yarn allocates more resources than what Samza requested on a specific host, the extra resources are added to a spare-pool called the "ANY_HOST Buffer". Later, when there is a resource request for the same host from Samza and Yarn does not return resources, we don't leverage the spare-pool of previously returned resources in that host.

This problem is specially pronounced in clusters that are heavily loaded in cpu, and memory where allocations need to satisfy both cpu and memory requirements of available hosts (Often, hosts have cpu but not memory or vice-versa). If there are a lot of container failures on a particular host in the midst of allocation, it further aggravates this problem.

The fix is as follows:
Check if there are available containers in the buffer corresponding to our preferred host. If not, we should also scan the ANY-HOST buffer for matched containers.