add flow ctrl hysteresis

with automatic nv, do not open nv before value is above
0.5 * (flowmax + flowstd)

tcl/startup/flow_ctrl.tcl

@@ -30,7 +30,17 @@ proc flow::loop {difget flowget flowset path flowstd flowlim} {
     set flowtarget $setval
   }
   putIntoLimits flowtarget $flowstd $flowlim
-  hupdate $path/flowtarget $flowtarget
+  set suppress_auto [silent 0 sct suppress_auto]
+  if {$suppress_auto || $flowtarget > ($flowstd + $flowlim) * 0.5} {
+    sct suppress_auto 0
+    hupdate $path/flowtarget $flowtarget
+  } else {
+    if {$flowtarget < $flowstd + 0.1} {
+      sct suppress_auto 1
+    } else {
+      hupdate $path/flowtarget $flowtarget
+    }
+  }
 }
 
 proc flow::bufferPut {path name var value} {