Don't test if symlink exists before 'rm -f'
When the symlink's target doesn't exist, '[ -f' is false, so the symlink doesn't get removed.
Since we do always want it to be removed, just call 'rm -f' anyway, which won't complain
if the file doesn't exist.
If and only if network setup because the container died, say so.
This involves capturing stderr output from all the 'ip' commands so we
can hide that output if we see the process died, or show it to the user
if the process didn't die, in which case we don't know why we failed.