GoXDCR CAPI (v1) high idle CPU and RAM usage

GoXDCR has very high CPU and RAM usage when in XDCR v1 (CAPI) mode even when the replication is idle. This behavior is consistently reproducible.

See attached screenshot on a system with a single 256MB bucket containing <10k docs and 0 op/s on the cluster. XDCR is configured to use 1 source and 1 target nozzle. The goxdcr process takes 1.5GB virual and ~500mb resident, and is consistently using ~30% CPU, which is as much CPU time as beam.smp and about twice as much as memcached.