Implemented a port allocator and a port mapper that is able to forward TCP ports
from the host to the container.
Upstream-commit: 799ffa176399877e610ff2049dbf84610037a2be
Component: engine
is assigned to each container upon Start and released whenever the
container exits.
Upstream-commit: c08f5b2b8460f13f2094bae2a496bf308f7645bb
Component: engine