[BUG] netlab capture does not work with vrnetlab containers

[ipspace]

The vrnetlab containers do not use the device interface names in the container network namespace. The container network namespace has the traditional ethx devices that are then mapped into the VM interfaces.

netlab capture checks the specified interface name, so you cannot specify ethx as the capture interface name, and tcpdump fails if you specify (for example) GigabitEthernet2 as the interface name.

Expected behavior

netlab capture has to treat the vrnetlab containers differently. It should recognize a vrnetlab container based on its container image name, allow ethx names (as in "the user knows what they're doing") or map the specified interface name into ethx based on interface ifindex.