It's been removed with #9597.

If panic mode failed to disable the specific device that couldn't be
spoofed (by unloading the module) we disable networking. Previously we
only stopped NetworkManager. The problem is that NM isn't even started
at this time, but will specifically be started when we're done with
MAC spoofing.

Therefore, let's remove NetworkManager so it cannot possibly be
started.

Will-fix: #10160

Fix-committed: #9890

Fix-committed: #9877

... so that we won't be nagged when testing Tails 1.5.1 (in
particular, that would break large parts of the automated test
suite). Apparently this was forgotten during the 1.5 release. Oops!

Fix-committed: #10112

Will-Fix: #10112