odrefresh: failure handling improvements

Add ExitCode::kCleanupFailed to report issues when removing files and
directories.

Add WARN_UNUSED to important methods to ensure their return values are
checked.

Remove LOG(FATAL) use in target code paths.

Remove TEMP_FAILURE_RETRY for calls that are not interruptable
according to their man page documentation (fchmod, unlink).

Bug: 160683548
Test: manual
Change-Id: I9681c83d048f4dd7988e9ff7ec1caf25ed02fbec
2 files changed