prebidServerBidAdapter - cookie_sync - ReferenceError: pbjsSyncsKey is not defined

[robertrmartinez]

BUG

Description

Prebid Server Adapter -> cookie_sync call:
When a cookie_sync call responds with "status":"ok" a reference error is thrown.
ReferenceError: pbjsSyncsKey is not defined

As @snapwich pointed out to me, the variable pbjsSyncsKey is referenced but never defined, see the following link:
https://github.com/prebid/Prebid.js/blame/d566700089066fce4a2b9400999360b246c0435a/modules/prebidServerBidAdapter.js#L249

Steps to Reproduce

Any cookie_sync call which responds with "status":"ok" will throw this error.