Fix id btree reduce function
Fix id btree reduce function

The number of deleted documents was being calculated
in a wrong way.

This relates to MB-5122 but doesn't fully fix it, there
are other issues elsewhere, as this id btree reduce function
is receiving doc info records with the deleted flag enabled
when it shouldn't be enabled.

Change-Id: I5f044520ac26ef7d270953f5c95632d0c18344a0
Reviewed-on: http://review.couchbase.org/15072
Reviewed-by: Jens Alfke <21e2afd93d5ce53123476032b5dca8a79b546094@couchbase.com>
Tested-by: Jens Alfke <21e2afd93d5ce53123476032b5dca8a79b546094@couchbase.com>
Reviewed-by: Damien Katz <99e6b749acbfbe2a596df99e91d24d6e1fdbee00@couchbase.com>

couchbaselabs/couchstore-specials,abhinavdangeti/couchstore,vmx/couchstore,hsharsha/couchstore,hsharsha/couchstore,couchbaselabs/couchstore-specials,couchbaselabs/couchstore,hsharsha/couchstore,vmx/couchstore,couchbaselabs/couchstore,t3rm1n4l/couchstore,t3rm1n4l/couchstore,couchbaselabs/couchstore,jimwwalker/couchstore,couchbaselabs/couchstore-specials,abhinavdangeti/couchstore,t3rm1n4l/couchstore,abhinavdangeti/couchstore,vmx/couchstore,couchbaselabs/couchstore-specials,hsharsha/couchstore,couchbaselabs/couchstore-specials,jimwwalker/couchstore,jimwwalker/couchstore