Index create is stuck at 50% build in testcase test_concurrent_mutations_index_create_query_drop

Run: http://qa.sc.couchbase.com/job/cen006-2i-vset01-00-basic-integration-tests/70/consoleFull

Build: 4.0.0-3312

In the above run, test_8 always fails with timeout while building index. In this particular run, the index that is stuck is: InstanceId: 9606927037220866739 Name: employee8f5ceb065bbf405195b0cb477cee8f70job_title_join_yr0_drop_candidates Bucket: default

From latest Index Stats:
"default:employee8f5ceb065bbf405195b0cb477cee8f70job_title_join_yr0_drop_candidates:num_docs_indexed":96768,
"default:employee8f5ceb065bbf405195b0cb477cee8f70job_title_join_yr0_drop_candidates:num_docs_pending":96768,

All logs attached at: https://s3-ap-southeast-1.amazonaws.com/indexing-test/logs/Jenkins/basic-integration-tests_Run70/

Live Cluster: http://172.23.106.75:8091/index.html#sec=indexes&logsTabs=1&collectInfoViewName=result