Set default lock to light-locker-command

Summary:
Instead of lxlock, which is not part of 18.04/18.04.1, set default lock to light-locker-command.

  * Depend on light-locker
  * Replace lxlock with light-locker-command -l
  * Added changelog entry

Test Plan:
1. Boot Lubuntu 18.04/18.04.1
2. Login
3. Delete ~/.config/lxsession/Lubuntu/desktop.conf
4. Logout
5. Login
6. Press CTRL-ALT-L

Reviewers: wxl, tsimonq2

Reviewed By: wxl, tsimonq2

Maniphest Tasks: T90

Differential Revision: https://phab.lubuntu.me/D23

debian/changelog

@@ -1,3 +1,10 @@
+lubuntu-default-settings (0.54.3) bionic; urgency=medium
+
+  * Set the default lock to light-locker-command instead of lxlock
+    (LP: #1812594)
+
+ -- apt-ghetto <apt-ghetto@lubuntu.me>  Thu, 25 Jul 2019 10:21:00 +0200
+
 lubuntu-default-settings (0.54.2) bionic; urgency=medium
 
   * Remove /usr/share/xsessions/QLubuntu.desktop from

src/etc/xdg/lxsession/Lubuntu/desktop.conf

@@ -55,6 +55,8 @@ im1/autostart=
 
 webcam/command=guvcview
 
+lock_manager/command=light-locker-command -l
+
 [State]
 laptop_mode=unknown
 

src/usr/share/applications/lubuntu-screenlock.desktop.in

@@ -2,6 +2,6 @@
 _Name=ScreenLock
 _Comment=Lock your screen
 Icon=system-lock-screen
-Exec=lxlock
+Exec=light-locker-command -l
 NoDisplay=true
 Type=Application