MB-17461 Adjust test_tap_rcvr_mutate to not malloc(0)
MB-17461 Adjust test_tap_rcvr_mutate to not malloc(0)

Resolves clang static analyzer warning

Change-Id: I9b492c6122a250516ea35831c00588d3b4ae3d2e
Reviewed-on: http://review.couchbase.org/59209
Reviewed-by: abhinav dangeti <d73ef2279de6577f7bf081737ee47554bbb7dc82@couchbase.com>
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

hisundar/ep-engine,membase/ep-engine,teligent-ru/ep-engine,owendCB/ep-engine,daverigby/ep-engine,daverigby/kv_engine,owendCB/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,membase/ep-engine,daverigby/kv_engine,daverigby/ep-engine,daverigby/ep-engine,owendCB/ep-engine,membase/ep-engine,hisundar/ep-engine,hisundar/ep-engine,teligent-ru/ep-engine,couchbase/ep-engine,couchbase/ep-engine,daverigby/kv_engine,owendCB/ep-engine,hisundar/ep-engine,couchbase/ep-engine,daverigby/ep-engine,daverigby/kv_engine,teligent-ru/ep-engine,membase/ep-engine