[XDCR] gomemcached memory consumption is not captured in memory profile

There was some work that was done as part of the planning effort for XDCR limits. As part of the planning effort, we discovered that gomemcached's memory allocation escapes the heap analysis for goxdcr. What this means is that the memory profiling for goxdcr will not show the memory allocated on the heap per gomemcached. As such, the mprof file will show much less memory usage than what the goxdcr RSS actually uses.

This is documented as part of the Couchbase-visible document https://docs.google.com/document/d/1tW75g1hA-iQnxJ_qlr7DPSZma-86c-Iyp7Ntivrue5w/edit#heading=h.pyp628m2542q