T6267: Check interface wireless module before apply config

Check if the wireless device/modem exists in the system and the
module `ieee802111` was loaded
In cases where we do not have wireless devices, it prevents the
unexpected traceback

```
set interfaces wireless wlan0 address 192.0.2.5/32
commit

Traceback (most recent call last):
  File "/usr/libexec/vyos/conf_mode/interfaces_wireless.py", line 269, in <modu>
    c = get_config()
        ^^^^^^^^^^^^
  File "/usr/libexec/vyos/conf_mode/interfaces_wireless.py", line 104, in get_cg
    tmp = find_other_stations(conf, base, wifi['ifname'])
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/libexec/vyos/conf_mode/interfaces_wireless.py", line 54, in find_os
    for phy in os.listdir('/sys/class/ieee80211'):
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/sys/class/ieee80211'
```

0 files changed, 0 insertions, 0 deletions