ScopedFd: Don't use TEMP_FAILURE_RETRY() with close()

According to the comments in Posix_close(), TEMP_FAILURE_RETRY() should
not be used with close():

https://android.googlesource.com/platform/libcore/+/462bdac45c10f43d88d8f07f6994e272a27c14a2%5E%21/#F12

Kill ScopedFd by simplifying the single caller.

Bug: http://b/20501816


Change-Id: I248c40b8c2fc95f1938a6edfc245c81847fc44af
Signed-off-by: Spencer Low <CompareAndSwap@gmail.com>
(cherry picked from commit 0346ad7a)