[GSI] test_oom_flush_bucket with indexer still in oom.

Steps:
1. Push one of the indexer oom.
2. Flush all the buckets in the cluster.
3. Verify indexer is online.

Error:
FAIL: test_oom_flush_bucket (2i.memdb_oom_2i.SecondaryIndexMemdbOomTests)
----------------------------------------------------------------------
Traceback (most recent call last):
File "pytests/2i/memdb_oom_2i.py", line 124, in test_oom_flush_bucket
self.assertFalse(self._validate_indexer_status_oom(), "Indexer still in OOM")
AssertionError: Indexer still in OOM

Testrunner Command:
./testrunner -i /tmp/centos_upgrade2i.ini get-cbcollect-info=True -t 2i.memdb_oom_2i.SecondaryIndexMemdbOomTests.test_oom_flush_bucket,gsi_type=memory_optimized,nodes_init=4,services_init=kv:n1ql-kv-index-index,doc_ops=True,standard_buckets=2,default_buckets=1,initial_index_number=2

Testrunner logs:
http://qa.sc.couchbase.com/job/cen006-2i-vset07-02-memdb-oom/44/consoleFull