Incorrect retry logic in OverlayDB::commit()

[tzubcic-tolar]

aleth/libdevcore/OverlayDB.cpp

Line 63 in 2fe1bec

m_db->commit(std::move(writeBatch));

Since writeBatch (which is a unique_ptr) is moved, if m_db->commit() throws, the next retry will attempt to call it with a unique_ptr that has been moved from.