Removed what seems to be the last of the calls to rand(). Closes #582.

src/rt/sync/sync.cpp

@@ -19,10 +19,6 @@ void sync::sleep(size_t timeout_in_ms) {
 #endif
 }
 
-void sync::random_sleep(size_t max_timeout_in_ms) {
-    sleep(rand() % max_timeout_in_ms);
-}
-
 rust_thread::rust_thread() : _is_running(false), thread(0) {
     // Nop.
 }

src/rt/sync/sync.h

@@ -5,7 +5,6 @@ class sync {
 public:
     static void yield();
     static void sleep(size_t timeout_in_ms);
-    static void random_sleep(size_t max_timeout_in_ms);
     template <class T>
     static bool compare_and_swap(T *address,
         T oldValue, T newValue) {

src/rt/test/rust_test_runtime.cpp

@@ -15,7 +15,7 @@ rust_domain_test::worker::run() {
     for (int i = 0; i < TASKS; i++) {
         handle->create_task(NULL, "child");
     }
-    sync::random_sleep(1000);
+    sync::sleep(rand(&handle->rctx) % 1000);
 }
 
 bool
@@ -62,6 +62,6 @@ rust_task_test::run() {
         worker->start();
     }
 
-    sync::random_sleep(1000);
+    sync::sleep(rand(&kernel.sched->rctx) % 1000);
     return true;
 }