Bug#944589: gsequencer: stalls system

[westlake <westlake2012@videotron.ca>]

I tested with bpo kernel 5.2.0-0.bpo.3-rt-amd64 and similar issue.

I notice there's a set_schedul* something message along with "operation 
not permitted"... that might provide a hint..

there's no ~/.gsequencer directory made yet, as the stall occurs either 
while still scanning ladspa or lv2 plugins.

The point of the stall is random but it occurs during the plugin-scan..

-- terminal text shows the point that it stalls is random..

Sometimes I am able to do Ctl-c, sometimes not and I need to do a hard 
shutdown (power button)..