Disable softrealtime (SCHED_ISO) and renice by default

SCHED_ISO is not supported by upstream kernels, so don't try to use this by
default since for most users it will result in an error log that trying to
set the scheduling policy fails.

Without extra system configuration, we will also not have permission to renice
processes by default, so out of the box doing this will fail as well.

Users that wish to use these features can enable them from the config once
they have configured their system appropriately.

daemon/daemon_config.c

@@ -326,7 +326,6 @@ static void load_config_files(GameModeConfig *self)
 
 	/* Set some non-zero defaults */
 	self->values.inhibit_screensaver = 1; /* Defaults to on */
-	self->values.renice = 4;              /* default value of 4 */
 	self->values.reaper_frequency = DEFAULT_REAPER_FREQ;
 	self->values.gpu_device = -1; /* 0 is a valid device ID so use -1 to indicate no value */
 	self->values.nv_powermizer_mode = -1;