Search domains are not considered for split-tunnelling connections

For split-tunnelling VPN connections (i.e. when the "Use only for resources on this connection" checkbox is set in the IPv4 -> Routes menu), the IPv4 -> Search Domains field has no effect.

For example, my VPN connection has the following parameters:

[ipv4]
dns=xxx.xxx.xxx.xxx;
dns-search=mydomain.net;
ignore-auto-dns=true
method=auto
never-default=true

After connecting, `systemd-resolve --status` shows for this connection:

Link 5 (tun0)
      Current Scopes: DNS
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: allow-downgrade
    DNSSEC supported: yes
         DNS Servers: xxx.xxx.xxx.xxx
          DNS Domain: ~mydomain.net

Note that there is a ~ character before the domain name, which has a special semantics in systemd-resolved (as I understand, such entries are not used as search names).

As a result, the search name is not used to complete simple names:

systemd-resolve foo
foo: resolve call failed: All attempts to contact name servers or networks failed
ping foo
ping: foo: Name or service not known
ping foo.mydomain.net
64 bytes from xxx.xxx.xxx.xxx (xxx.xxx.xxx.xxx): icmp_seq=1 ttl=62 time=5.33 ms

Note that the search domains work if the VPN connection is configured as non-split-tunnelling connection. In this case `systemd-resolve --status` shows "DNS Domain: mydomain.net" (without ~) and `systemd-resolve foo` and `ping foo` work as expected.

ProblemType: Bug
DistroRelease: Ubuntu 17.04
Package: network-manager 1.4.4-1ubuntu3
Uname: Linux 4.9.0-22.1-liquorix-amd64 x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.20.4-0ubuntu4
Architecture: amd64
CurrentDesktop: KDE
Date: Tue Apr 18 18:46:53 2017
IfupdownConfig:
 # interfaces(5) file used by ifup(8) and ifdown(8)
 auto lo
 iface lo inet loopback
InstallationDate: Installed on 2015-05-01 (717 days ago)
InstallationMedia: Kubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
NetworkManager.state:
 [main]
 NetworkingEnabled=true
 WirelessEnabled=true
 WWANEnabled=true
RfKill:
 0: hci0: Bluetooth
  Soft blocked: no
  Hard blocked: no
SourcePackage: network-manager
UpgradeStatus: Upgraded to zesty on 2017-04-16 (2 days ago)
mtime.conffile..etc.NetworkManager.NetworkManager.conf: 2017-04-18T18:41:39.752743
nmcli-nm:
 RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN
 running 1.4.4 connected started full enabled enabled enabled enabled enabled