init: more header cleanup

Remove includes of "log.h" that really want <android-base/logging.h>
Fix header include order
Remove headers included in .cpp files that their associated .h already includes
Remove some unused headers

Test: boot bullhead
Change-Id: I2b415adfe86a5c8bbe4fb1ebc53c7b0ee2253824
diff --git a/init/reboot.h b/init/reboot.h
index 3956249..6432fa5 100644
--- a/init/reboot.h
+++ b/init/reboot.h
@@ -17,6 +17,8 @@
 #ifndef _INIT_REBOOT_H
 #define _INIT_REBOOT_H
 
+#include <string>
+
 /* Reboot / shutdown the system.
  * cmd ANDROID_RB_* as defined in android_reboot.h
  * reason Reason string like "reboot", "userrequested"