[Windows] memory fragmentation ratio (mem_used / total_heap_bytes) increased from 10% (2.5.1) to 14% (3.0.2) with append based workload

Test case:kv_fragmentation_revAB_100K.test
Fragmentation % went up fro 10.5(2.5.1) to 13.5(3.0.1)

Number of items:100K
Bucket RAM quota:20480MB
resident ratio:100%
hardware: 12 vCPU, 32 GB,HDD

links:
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=arjuna_301-1437_cbc_load
http://cbmonitor.sc.couchbase.com/reports/html/?snapshot=arjuna_251-1083_0a7_load

logs:
3.0.1:
http://ci.sc.couchbase.com/job/arjuna/5/artifact/172.23.100.44.zip
http://ci.sc.couchbase.com/job/arjuna/5/artifact/172.23.100.45.zip
http://ci.sc.couchbase.com/job/arjuna/5/artifact/172.23.100.55.zip
http://ci.sc.couchbase.com/job/arjuna/5/artifact/172.23.100.56.zip
2.5.1:
http://ci.sc.couchbase.com/job/arjuna/6/artifact/172.23.100.44.zip
http://ci.sc.couchbase.com/job/arjuna/6/artifact/172.23.100.45.zip
http://ci.sc.couchbase.com/job/arjuna/6/artifact/172.23.100.55.zip
http://ci.sc.couchbase.com/job/arjuna/6/artifact/172.23.100.56.zip