Always use --quiet when running `systemctl is-active i2p'.

This is what we do everywhere else in our code base.

refs: #10684

config/chroot_local-includes/usr/local/sbin/tails-i2p

@@ -77,7 +77,7 @@ case "${1}" in
     start|restart)
         # Stop I2P before setting the router console language in case
         # it pushes any updated options on quit.
-        if systemctl is-active i2p; then
+        if systemctl --quiet is-active i2p; then
             systemctl stop i2p
         fi
         # Get LANG, since we may run this from an environment that

features/step_definitions/i2p.rb

 Given /^I2P is (?:still )?(not )?running$/ do |notrunning|
   if notrunning
-    !$vm.execute('systemctl is-active i2p').success?
+    !$vm.execute('systemctl --quiet is-active i2p').success?
   else
     try_for(60) do
-      $vm.execute('systemctl is-active i2p').success?
+      $vm.execute('systemctl --quiet is-active i2p').success?
     end
   end
 end