Remove unused FileDescriptor::Reset().

The Reset() method was not directly used anywhere.

BUG=b:34284069
TEST=Ran unittests. grep for 'Reset()' in update_engine.

Change-Id: I8db0f17c43a36b03acbc22cdfa35a3e6042c3e75
(cherry picked from commit 4a53c76795b4df0a4ea6636ee740371ffe83d7b4)
Reviewed-on: https://chromium-review.googlesource.com/641956
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>
diff --git a/payload_consumer/file_descriptor.cc b/payload_consumer/file_descriptor.cc
index 8a23dea..ebe4428 100644
--- a/payload_consumer/file_descriptor.cc
+++ b/payload_consumer/file_descriptor.cc
@@ -127,12 +127,8 @@
   CHECK_GE(fd_, 0);
   if (IGNORE_EINTR(close(fd_)))
     return false;
-  Reset();
-  return true;
-}
-
-void EintrSafeFileDescriptor::Reset() {
   fd_ = -1;
+  return true;
 }
 
 }  // namespace chromeos_update_engine