dpms/wayland: Explicitly set as unsupported if addRegistryListener didn't find the interface
If a org_kde_kwin_dpms_manager wasn't found, setSupported(false) so that the user gets closure.
(cherry picked from commit 160fff73)
If a org_kde_kwin_dpms_manager wasn't found, setSupported(false) so that the user gets closure.
(cherry picked from commit 160fff73)