overlay/live: reconfigure NetworkManager-wait-online in the real root

This adds coreos-liveiso-reconfigure-nm-wait-online.service which will
configured NetworkManager-wait-online.service in the real root timeout
quicker and also not show a failure if there is no connection.

Doing this for the Live ISO improves the user experience when booting
the Live ISO without network.

overlay.d/05core/usr/lib/dracut/modules.d/20live/coreos-liveiso-reconfigure-nm-wait-online.service

@@ -0,0 +1,23 @@
+# Configure NetworkManager-wait-online in the real root for the
+# Live ISO to timeout quicker and also not explicitly fail since
+# booting the Live ISO without network is a valid use case.
+#
+# Doing this improves the user experience when booting the
+# Live ISO without network.
+
+[Unit]
+Description=Reconfigure NetworkManager-wait-online service
+DefaultDependencies=no
+# Make sure we are in the initramfs and we are booted to the live ISO
+ConditionPathExists=/usr/lib/initrd-release
+ConditionKernelCommandLine=coreos.liveiso
+ConditionPathExists=/run/ostree-live
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+# Note keep this in sync with NetworkManager-wait-online.service
+# Right now we are keeping the same ExecStart but we are making it
+# OK to fail (`-`) and timeout sooner (5 seconds vs 30).
+ExecStartPre=/usr/bin/mkdir -p /run/systemd/system/NetworkManager-wait-online.service.d
+ExecStart=/bin/bash -c 'echo -e "[Service]\nExecStart=\nExecStart=-/usr/bin/nm-online -s -q --timeout=5" > /run/systemd/system/NetworkManager-wait-online.service.d/liveiso.conf'

overlay.d/05core/usr/lib/dracut/modules.d/20live/live-generator

@@ -28,6 +28,7 @@ add_requires sysroot-etc.mount initrd-root-fs.target
 add_requires sysroot-var.mount initrd-root-fs.target
 
 add_requires coreos-liveiso-network-kargs.service              initrd.target
+add_requires coreos-liveiso-reconfigure-nm-wait-online.service initrd.target
 
 mkdir -p "${UNIT_DIR}/ostree-prepare-root.service.d"
 cat > "${UNIT_DIR}/ostree-prepare-root.service.d/10-live.conf" <<EOF