The filesystem driver has been migrated to impleemnt the storagedriver
interface changes. Most interetingly, this provides a filesystem-based
implementation of the Stat driver call. With this comes some refactoring of
Reads and Write to be much simpler and more robust.
The IPC tests have been disabled to stability problems that we'll have to
troubleshoot at a later date.
This change brings the storagedriver API in line with the Go standard library's
use of int64 for offsets. The main benefit is simplicity in interfacing with
the io library reducing the number of type conversions in simple code.
Fixes/tests listing for keys beginning with "/"
No longer extraneously wraps Closers in ioutil.NopClosers
Uses omitempty for all ipc struct type fields
This only works for a specific whitelist of error types, which is
currently all errors in the storagedriver package.
Also improves storagedriver tests to enforce proper error types are
returned
