MB-8357 Don't merge view log files

During the view compaction retry phase, don't merge the
log files, as these can result in stale and no longer valid
KV pairs in the view btrees in some circumstances.

This issue happens only when during the initial view compaction
phase multiple view updates happen, each update gets a new
version of the same documents and each document version produces
a different key than before. Because btree operations are sorted
by key and then by operation (insert or remove), this results
in stale (no longer valid) and current KV pairs to end up in view
btrees. For example, lets say there's 2 log files for a view btree,
each with the following contents:

File 1: [ {insert, {Key1, DocId_A}, Value1} ]
File 2: [ {remove, {Key1, DocId_A}}, {insert, {Key2, DocId_A}, Value2} ]

After those 2 files are merged, we ended up with a file having the
following operations:

[ {remove, {Key1, DocId_A}}, {insert, {Key1, DocId_A}, Value1}, {insert, {Key2, DocId_A}, Value2} ]

Which would cause the corresponding view btree to have stale data
besides current and valid data.

Change-Id: I19a71bfa7dd754376500361b1ea76afb57e22ece
Reviewed-on: http://review.couchbase.org/26821
Reviewed-by: Chris Anderson <jchris@couchbase.com>
Reviewed-by: Damien Katz <damien@couchbase.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>
Merge remote-tracking branch 'origin/2.1.0' into 2.1.1

* origin/2.1.0:
  MB-8357 Don't merge view log files

Change-Id: I3a24e1d8d74166dae203ad2e3b3815e03841d5bc