CBQE-0: remove unused variables from CompactionTests.cc

Change-Id: I8147e3c4991805d52c261a8a4cdffa254f8000d7
Reviewed-on: http://review.couchbase.org/44087
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>