Switch fastboot/init/libprocessgroup to std::this_thread::sleep_for.

Bug: http://b/32878766
Test: boots
Change-Id: Ie0ddfb7e60f2da5f6eefbb10c83a92e88c137ae3
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index 4cd423a..7f4a0dd 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -43,7 +43,9 @@
 #include <sys/types.h>
 #include <unistd.h>
 
+#include <chrono>
 #include <functional>
+#include <thread>
 #include <utility>
 #include <vector>
 
@@ -301,7 +303,7 @@
             announce = false;
             fprintf(stderr, "< waiting for %s >\n", serial ? serial : "any device");
         }
-        usleep(1000);
+        std::this_thread::sleep_for(std::chrono::milliseconds(1));
     }
 }