Revert "init: use read_file and write_file to implement do_copy builtin"

This reverts commit 82bac0de6d95bcdf45729516f6a4f29eb2681118.

Change-Id: Ibfdf453bd85ba4fcd1948b78bd22e639a883653e
diff --git a/init/util.cpp b/init/util.cpp
index 9b02de2..c987181 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -184,8 +184,8 @@
 }
 
 bool write_file(const char* path, const char* content) {
-    android::base::unique_fd fd(TEMP_FAILURE_RETRY(
-        open(path, O_WRONLY | O_CREAT | O_NOFOLLOW | O_TRUNC | O_CLOEXEC, 0600)));
+    android::base::unique_fd fd(
+        TEMP_FAILURE_RETRY(open(path, O_WRONLY | O_CREAT | O_NOFOLLOW | O_CLOEXEC, 0600)));
     if (fd == -1) {
         PLOG(ERROR) << "write_file: Unable to open '" << path << "'";
         return false;