modem/broadband: set the gsm.device-id in complete_connection()

This is the preferred way of associating the connection with a
particualr modem.
12 jobs for lr/modem-device-id in 31 minutes and 53 seconds (queued for 48 seconds)
latest
Status Job ID Name Coverage
  Test
passed #285846
allowed to fail
checkpatch

00:00:56

passed #285853
t_debian:9

00:14:47

passed #285855
t_debian:sid

00:14:29

manual #285854
allowed to fail manual
t_debian:testing
passed #285847
t_fedora:28

00:31:06

passed #285848
t_fedora:29

00:28:37

passed #285849
t_fedora:30

00:21:33

manual #285850
allowed to fail manual
t_fedora:rawhide
passed #285851
t_ubuntu:16.04

00:15:38

passed #285852
t_ubuntu:18.04

00:14:20

 
  External
failed NetworkManager test verification

failed NetworkManager test verification

06:31:59