wifi: set the BridgeIfname supplicant property when needed

When a wifi device is in a bridge, the supplicant must be aware of it,
as a socket must be opened on the bridge to receive packets.

Set the BridgeIfname property of the supplicant Interface object
before starting the association. Note that the property was read-only
in the past and recently [1] became read-write. When using a
supplicant version without the patch, writing the property will return
an InvalidArgs error and NetworkManager will print a warning.

[1] https://w1.fi/cgit/hostap/commit/?id=1c58317f56e312576b6872440f125f794e45f991

#83
22 jobs for bg/wifi-bridge in 35 minutes and 2 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #4976336
checkpatch

00:02:00

manual #4976344
allowed to fail manual
t_centos:7.5.1804
manual #4976345
allowed to fail manual
t_centos:7.6.1810
manual #4976346
allowed to fail manual
t_centos:7.7.1908
manual #4976347
allowed to fail manual
t_centos:7.8.2003
manual #4976348
allowed to fail manual
t_centos:8.1.1911
manual #4976354
allowed to fail manual
t_debian:10
manual #4976353
allowed to fail manual
t_debian:9
manual #4976356
allowed to fail manual
t_debian:sid
manual #4976355
allowed to fail manual
t_debian:testing
manual #4976337
allowed to fail manual
t_fedora:28
manual #4976338
allowed to fail manual
t_fedora:29
manual #4976339
allowed to fail manual
t_fedora:30
manual #4976340
allowed to fail manual
t_fedora:31
passed #4976341
t_fedora:32

00:35:02

manual #4976342
allowed to fail manual
t_fedora:33
manual #4976343
allowed to fail manual
t_fedora:rawhide
manual #4976349
allowed to fail manual
t_ubuntu:16.04
manual #4976350
allowed to fail manual
t_ubuntu:18.04
manual #4976352
allowed to fail manual
t_ubuntu:devel
manual #4976351
allowed to fail manual
t_ubuntu:rolling
 
  External
canceled https://desktopqe-jenkins.rhev-ci-vms.eng.rdu2.redhat.com/job/beaker-NetworkManager-gitlab-trigger-code-upstream/1877/

489:14:28