Fix an endless loop when getrandom is not available

tbu- · tbu- · commit b95c491dfc77 · 2018-09-02T00:19:11.000+02:00
diff --git a/src/libstd/sys/unix/rand.rs b/src/libstd/sys/unix/rand.rs
@@ -61,6 +61,7 @@ mod imp {
                     continue;
                 } else if err == libc::ENOSYS {
                     GETRANDOM_UNAVAILABLE.store(true, Ordering::Relaxed);
+                    return false;
                 } else if err == libc::EAGAIN {
                     return false;
                 } else {
