[SPARK-20404][CORE] Using Option(name) instead of Some(name)

Using Option(name) instead of Some(name) to prevent runtime failures when using accumulators created like the following
```
sparkContext.accumulator(0, null)
```

Author: Sergey Zhemzhitsky <szhemzhitski@gmail.com>

Closes #17740 from szhem/SPARK-20404-null-acc-names.

(cherry picked from commit 0bc7a902)
Signed-off-by: Sean Owen <sowen@cloudera.com>