DCP observe regression between 4.5.1 build 2727 and 2756

As part of running the daily sanity test the dcp observe test went from an expected 4.5 msec to 16 msec between builds 903 and 913. I see 3 possible culprits:

• http://review.couchbase.org/65394 (904)
• http://review.couchbase.org/65988 (908)
• http://review.couchbase.org/66050 (913)

If one of these stands out as the cause I can test with the immediate prior build.

This is also seen in 4.5.1 between build 2727 and 2756 though I did not see any changes there which intersected with the Spock changes.