MB-9307: Add rollback to couch_upr

Add the rollback response to the couch_upr_fake_server when
the sequence number is too high. Also handle that case in
couch_upr.

Change-Id: Idf09828f29e6edc766d004a1f62f98f789d29f48
Reviewed-on: http://review.couchbase.org/29416
Reviewed-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Volker Mische <volker.mische@gmail.com>