Fix socket detection

* Some research is needed to find a better version, but the current
  implementation does not work when the socket is already stopped
  or YaST is running on 1st stage.

library/systemd/src/modules/systemd_service.rb

@@ -190,19 +190,13 @@ def restart
 
       # Returns socket associated with service or nil if there is no such socket
       #
+      # @note The current implementation is too simplistic. At this point, checking the
+      # 'Triggers' property of each socket would be a better way. However, it won't work
+      # during installation as 'systemctl show' is not available.
+      #
       # @return [Yast::SystemdSocketClass::Socket]
       def socket
-        return @socket if @socket
-
-        # not triggered
-        socket_name = properties.triggered_by
-        return unless socket_name
-
-        # this may be a space separated list
-        socket_name = socket_name[/\S+\.socket/]
-        return unless socket_name # triggered by non-socket
-
-        @socket = Yast::SystemdSocket.find(socket_name)
+        @socket ||= Yast::SystemdSocket.find(name)
       end
 
       # Determines whether the service has an associated socket

library/systemd/test/systemd_service_test.rb

@@ -179,20 +179,22 @@ module Yast
 
     describe "#socket" do
       subject(:service) { SystemdService.find(service_name) }
+      let(:service_name) { "sshd" }
 
-      before { stub_services(service: service_name) }
+      before do
+        allow(SystemdSocket).to receive(:find).with(service_name).and_return(socket)
+      end
 
-      context "when the service is triggered by a socket" do
-        let(:service_name) { "cups" }
+      context "when a socket named after the service exists" do
+        let(:socket) { instance_double(SystemdSocketClass::Socket) }
 
         it "returns the socket" do
-          expect(service.socket).to be_a(Yast::SystemdSocketClass::Socket)
-          expect(service.socket.unit_name).to eq("iscsid")
+          expect(service.socket).to eq(socket)
         end
       end
 
-      context "when the service is not triggered by a socket" do
-        let(:service_name) { "sshd" }
+      context "when no socket named after the service exists" do
+        let(:socket) { nil }
 
         it "returns nil" do
           expect(service.socket).to be_nil
@@ -201,20 +203,22 @@ module Yast
     end
 
     describe "#socket?" do
-      subject(:service) { SystemdService.find(service_name) }
+      subject(:service) { SystemdService.find("sshd") }
 
-      before { stub_services(service: service_name) }
+      before do
+        allow(service).to receive(:socket).and_return(socket)
+      end
 
       context "when there is an associated socket" do
-        let(:service_name) { "cups" }
+        let(:socket) { instance_double(SystemdSocketClass::Socket) }
 
         it "returns true" do
           expect(service.socket?).to eq(true)
         end
       end
 
       context "when there is no associated socket" do
-        let(:service_name) { "sshd" }
+        let(:socket) { nil }
 
         it "returns false" do
           expect(service.socket?).to eq(false)