Comment 0 for bug 1875411

Hi,
First of all, I don't know if this bug is related to the new ubuntu 20.04 ecosystem or to the new netplan version.

The problem arises when we try to rename a network interface, for example with this config file:
```
network:
  version: 2
  ethernets:
    ens4:
      accept-ra: no
      dhcp4: false
      match:
        macaddress: fa:16:3e:b5:71:18
      set-name: uplink
```

The same configuration works on ubuntu 19.10 with netplan 0.98-0ubuntu1, but fails on ubuntu 20.04 with netplan 0.99-0ubuntu2 with the error:
```~# netplan apply
Traceback (most recent call last):
  File "/usr/sbin/netplan", line 23, in <module>
    netplan.main()
  File "/usr/share/netplan/netplan/cli/core.py", line 50, in main
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 179, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/apply.py", line 46, in run
    self.run_command()
  File "/usr/share/netplan/netplan/cli/utils.py", line 179, in run_command
    self.func()
  File "/usr/share/netplan/netplan/cli/commands/apply.py", line 162, in command_apply
    subprocess.check_call(['ip', 'link', 'set',
  File "/usr/lib/python3.8/subprocess.py", line 364, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['ip', 'link', 'set', 'dev', 'ens4', 'name', 'uplink']' returned non-zero exit status 2.
```

At this time, the fix is to set the interface down, and apply netplan conf again.

Cheers