Should not panic on insufficient container ID length

[lumjjb]

Currently, a error is throw due to insufficient ID length. However, this is not a good way to ensure uniqueness of tap names (and on hindsight is actually counterintuitive). Instead, a hash of the container ID should be done and the slice (tap + hash)[:syscall.IFNAMSIZ-1] should be used instead.

The requirement for this is that the process to determine the name should be deterministic. Which using a standard hash function should be able to provide.

https://github.com/nabla-containers/runnc/blob/master/libcontainer/factory_nabla.go#L98

[lumjjb]

@InTheCloudDan is working on this! :)

[lumjjb]

New code location is https://github.com/nabla-containers/runnc/blob/master/llmodules/network/tap_bridge.go#L77-L83