mmcli,modem: new `--inhibit` action on the modem object

Modem device inhibition is really a manager action for which we
provide the full modem device 'uid'.

This new operation allows to perform device inhibition using the modem
object as reference, which is more handy than first looking at the
device 'uid' and then running the manager action.

    $ sudo mmcli -m 0 --inhibit
    successfully inhibited device with uid '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-12/1-12.2'
    type Ctrl+C to abort this program and remove the inhibition
    ^C cancelling the operation...
    successfully uninhibited device with uid '/sys/devices/pci0000:00/0000:00:14.0/usb1/1-12/1-12.2'
1 file changed