container: expose priority and SCHED_OTHER policy

The more explicit API removes the arbitrary limit preventing use of SCHED_OTHER (referred to as SCHED_NORMAL in the kernel). This change also exposes priority value to set.

Signed-off-by: Ophestra <cat@gensokyo.uk>

container/std/syscall.go

@@ -134,7 +134,7 @@ func (policy SchedPolicy) GetPriorityMax() (Int, error) {
 			0, 0,
 		)
 		schedPriority[policy][0] = Int(priority)
-		if schedPriority[policy][0] < 0 {
+		if errno != 0 {
 			schedPriorityErr[policy][0] = errno
 		}
 	})
@@ -151,10 +151,9 @@ func (policy SchedPolicy) GetPriorityMin() (Int, error) {
 			0, 0,
 		)
 		schedPriority[policy][1] = Int(priority)
-		if schedPriority[policy][1] < 0 {
+		if errno != 0 {
 			schedPriorityErr[policy][1] = errno
 		}
 	})
 	return schedPriority[policy][1], schedPriorityErr[policy][1]
-
 }