Import patches-unapplied version 2.518 to ubuntu/bionic-proposed

Imported using git-ubuntu import.

Changelog parent: 7f7f42d61d

New changelog entries:
  * Make subiquity installer boot quicker, by making dhcp interfaces
    optional, such that wait-online is not blocking bringing up the
    installer UI.

debian/changelog

@@ -1,3 +1,11 @@
+livecd-rootfs (2.518) bionic; urgency=medium
+
+  * Make subiquity installer boot quicker, by making dhcp interfaces
+    optional, such that wait-online is not blocking bringing up the
+    installer UI.
+
+ -- Dimitri John Ledkov <xnox@ubuntu.com>  Tue, 03 Apr 2018 14:56:58 +0100
+
 livecd-rootfs (2.517) bionic; urgency=medium
 
   [ Simon Quigley ]

live-build/ubuntu-server/includes.binary/overlay/etc/netplan/00-installer-config.yaml

@@ -7,7 +7,9 @@ network:
             match:
                 name: "en*"
             dhcp4: true
+            optional: true
         all-eth:
             match:
                 name: "eth*"
             dhcp4: true
+            optional: true