proc: bugs setting next breakpoints

1. A running goroutine is by definition not parked waiting for a
chan recv
2. The FDE end address is intended to be exclusive, the code
interpreted as inclusive and sometimes ended up setting a breakpoint
on a function other than the current one.

proc/variables.go

@@ -311,7 +311,7 @@ func (scope *EvalScope) PtrSize() int {
 // ChanRecvBlocked returns whether the goroutine is blocked on
 // a channel read operation.
 func (g *G) ChanRecvBlocked() bool {
-	return g.WaitReason == chanRecv
+	return (g.thread == nil) && (g.WaitReason == chanRecv)
 }
 
 // chanRecvReturnAddr returns the address of the return from a channel read.