Bug 1604973 - Install iproute2 in the mozlint docker image r=jmaher

Fix a test which calls the ip address
testing/mozbase/moznetwork/tests/test_moznetwork.py

Differential Revision: https://phabricator.services.mozilla.com/D58192

--HG--
extra : moz-landing-system : lando

taskcluster/docker/lint/system-setup.sh

@@ -11,6 +11,7 @@ cd /setup
 
 apt_packages=()
 apt_packages+=('curl')
+apt_packages+=('iproute2')
 apt_packages+=('locales')
 apt_packages+=('git')
 apt_packages+=('python')