Replace tabs with spaces

Change-Id: I47613d06dc34d1bfd854d1fac2a9099cb07f20ca
Reviewed-on: http://review.couchbase.org/27890
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Filipe David Borba Manana <fdmanana@gmail.com>