[system test] Index compaction is very slow on some indexes

1. load data + indexes
2. remove index node
3. add index node
4. rebuild indexes on the newly added node

Of the 7 new indexes built , 2 indexes show odd compaction activity.

• index tax_seq is at 49% fragmentation, and is showing no compaction activity.
• index flight_direction, 86% fragmentation, is very slowly compacting , about 1 MB every few seconds.
  The index file is 15G and it will take a very long amount of time for this to compact.

Verified the above by index file sizes on the machine

[root@centos-64-x64 default_tax_seq_2920987701092749433_0.index]# ls -lth
total 5.5G
rw-rw---. 1 couchbase couchbase 116M Aug 5 15:54 data.fdb.7
rw-rw---. 1 couchbase couchbase 5.5G Aug 5 15:50 data.fdb.6

and Compacting searches on the index logs.