MB-11917: Use couchbase-patched Erlang for Sherlock testing

Change-Id: Icd091c877a04b0a065c83052d75d26eeb64efdcc
Reviewed-on: http://review.couchbase.org/44007
Reviewed-by: Sriram Melkote <siri@couchbase.com>
Tested-by: Sriram Melkote <siri@couchbase.com>