rackerlabs/deuce — pull request #210 by TheSriram (2014-11-10 21:30:12+00:00)
Title: fix: x-ref modified for mongo and sqlite

- the sqlite driver needed a way to decrement references of block when a
file is deleted, by adding this functionality, the changes in
x-ref-modified were also taken care of.

- the mongo driver now has functionality for changing 'x-ref-modified'
time, both when the block is assigned to a file, and when a file gets
deleted (while having blocks assigned to it)

- bugfix: mongo driver when getting an orphaned block from blockstorage.
the fix here was to include the scenario, when the metadata_block_id
was not present in metadata ( as is the case with orphaned blocks)