tests: cover interface rename + IPv6 + flags for netns ops
tests: cover interface rename + IPv6 + flags for netns ops

Bug-Url: https://github.com/svinota/pyroute2/issues/84
tomislacker/python-iproute2,tomislacker/python-iproute2,nazarewk/pyroute2,little-dude/pyroute2,simudream/pyroute2,roolebo/pyroute2,vodik/pyroute2,roolebo/pyroute2,simudream/pyroute2,nazarewk/pyroute2,little-dude/pyroute2,mtiny/pyroute2,little-dude/pyroute2,vodik/pyroute2,drzaeus77/pyroute2,mtiny/pyroute2,nazarewk/pyroute2,drzaeus77/pyroute2