storvsc: use correct defaults for values determined by protocol negotiation

Use correct defaults for values determined by protocol negotiation,
instead of resetting them with every scsi controller.

Tested-by: Alex Ng <alexng@microsoft.com>
Signed-off-by: Keith Mange <keith.mange@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: James Bottomley <JBottomley@Odin.com>