DataStoreBlobStore should expose a buffer input stream for getInputStream call

DataStoreBlobStore directly exposes the InputStream from the wrapped DataStore. In most cases underlying DataStore exposes a LazyFileInputStream [0] which is not buffered.

For performance reason the stream finally exposed at the BlobStore layer should be buffered one. See [1] for the discussion

[1] http://markmail.org/thread/xi4isnzw57vphcsq
[0]
https://github.com/apache/jackrabbit/blob/trunk/jackrabbit-data/src/main/java/org/apache/jackrabbit/core/data/LazyFileInputStream.java#L102