rt: Remove some stack-wasting macros from rust_task::yield

Author: brson

src/lib/task.rs

@@ -146,6 +146,7 @@ time_in_us - maximum number of microseconds to yield control for
 fn sleep(time_in_us: uint) {
     let task = rustrt::rust_get_task();
     let killed = false;
+    log #fmt("yielding for %u us", time_in_us);
     rusti::task_sleep(task, time_in_us, killed);
     if killed {
         fail "killed";

src/rt/rust_task.cpp

@@ -268,11 +268,7 @@ rust_task::grow(size_t n_frame_bytes)
 // Only run this on the rust stack
 void
 rust_task::yield(size_t time_in_us, bool *killed) {
-    LOG(this, task, "task %s @0x%" PRIxPTR " yielding for %d us",
-        name, this, time_in_us);
-
     if (this->killed) {
-        A(sched, !blocked(), "Shouldn't be blocked before failing");
         *killed = true;
     }