Default value of [filter:slo] max_manifest_size was changed in swift[1]
but puppet-swift still hard-codes the old default.
This change updates the default value to use the consistent value.
[1] 11bf9e45884aa5122e76a97cf62062d7b0bdfe54
Change-Id: Iba68f63dcf5dc401cbbf2d396530a66157ad8fce