[SRU precise/trusty/utopic] LP#1400289 Hyper-V: drivers:scsi:storvsc: Fix a bug in handling ring buffer failures that may result in I/O freeze

[Andy Whitcroft]

Microsoft are reporting issues with raid setup over virtual drives attached
to the Hyper-V storvsc are hanging occasionally.  This has been tracked
to bad error handing when bounce buffers are not in use.  They have
requested the application of the following fix.

Proposing for SRU to precise, trusty, and utopic.

-apw