Upgrade to SPY 2.9.1

Change-Id: I615ec7a305c2177810e4307f41cd21a68d083a9a
Reviewed-on: http://review.couchbase.org/27214
Reviewed-by: Matt Ingenthron <matt@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>