Fix StorageService.partition() to always close RandomAccessFile writers

[iamsanjaymalakar]

Problem

StorageService.partition() creates multiple RandomAccessFile writers but closes them via a forEach wrapper that can throw early. If one close() fails (or if an exception occurs during reading/writing), remaining writers may not be closed.

Fix

Move writer cleanup into a finally block so all RandomAccessFile instances are always closed. Close failures are aggregated (first exception thrown, subsequent ones suppressed).