MB-100: Remove obsolete files from project

Looks like the following file no longer exist in the project.
mutation_log_compactor.cc
statsnap.cc

Change-Id: Idf7fcdb1a6b2e06b1e6e92edd46f03433cd37113
Reviewed-on: http://review.couchbase.org/26199
Reviewed-by: Michael Wiederhold <mike@couchbase.com>
Tested-by: Bin Cui <bin.cui@gmail.com>