When switching to VT, the ioctl DRM_DROP_MASTER must be done before the ioctl VT_RELDISP. Otherwise the kernel can't change the modesetting reliably, and this leads to the console not showing up in some cases, like after unplugging a docking station with a DP or HDMI monitor.
Before doing the VT_RELDISP, send a dbus message to logind, to pause the drm device, so logind will do the ioctl DRM_DROP_MASTER.
With this patch, it changes the order logind will send the resume event, and drm will be sent last instead of first. so there is a also fix to call systemd_logind_vtenter() at the right time.