Use const auto&/auto&& in adb.

Change-Id: I74a7e511302e15e207906f572d181634e0ed5604
diff --git a/adb_auth_host.cpp b/adb_auth_host.cpp
index 7b314c3..5309519 100644
--- a/adb_auth_host.cpp
+++ b/adb_auth_host.cpp
@@ -368,7 +368,7 @@
         return;
     }
 
-    for (auto& path : android::base::Split(adb_keys_path, ENV_PATH_SEPARATOR_STR)) {
+    for (const auto& path : android::base::Split(adb_keys_path, ENV_PATH_SEPARATOR_STR)) {
         if (!read_key(path.c_str(), key_list)) {
             D("Failed to read '%s'", path.c_str());
         }