For quite some time, Fedora has been shipping XFCE with a Fedora patch adding Ctrl-Alt-L as a default keyboard shortcut for xfce4-session-logout (unfortunately, this doesn't appear to have been discussed with the XFCE project).  After XFCE closed bug #10728, the XFCE build provided by Fedora 22 ended up with the same keyboard shortcut being assigned to different actions, xfce4-session-logout and xflock4.  Pressing Ctrl-Alt-L in the Fedora 22 XFCE Spin seems to randomly choose between showing the logout dialog and locking the screen (the latter is pretty annoying when you are in a hurry to reboot).

Of course, this is a Fedora problem [2], and it probably needs to be fixed there.  Would you perhaps consider adding a default keyboard shortcut for xfce4-session-logout?  Then Fedora could simply adopt that, without any custom patches carrying the risk of future conflicts.

Currently, XFCE maps both Ctrl-Alt-Delete and Ctrl-Alt-L to xflock4.  Perhaps Ctrl-Alt-Delete would be a good candidate for triggering xfce4-session-logout instead?  This would be consistent with the behavior in Gnome 3, KDE and even Windows: you can use Super-L to lock the screen and Ctrl-Alt-Delete to invoke some sort of logoff or poweroff dialog in both Gnome 3 and Windows (at least in 2000 and XP); Gnome migrated many of the older shortcuts using Ctrl-Alt to use Super [1], which is easier to type (especially for users with disabilities), but I think Ctrl-Alt-L continues to lock the screen in Gnome and probably KDE.

[1] https://help.gnome.org/users/gnome-help/stable/shell-keyboard-shortcuts.html.en
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1229218