Add initialization of c->wbytes during log shipping

Change-Id: I0605f6a58b2e7f41422f0ed53a14f297cfb2df25
Reviewed-on: http://review.couchbase.org/33251
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Tested-by: Trond Norbye <trond.norbye@gmail.com>