Remove helper method call from cohdistributed class

The helper call addcachebase is called by default when including the
module PuppetX::Type::CohCacheBase. Calling it again causes two
parameters of the same name attempt to be created. Ruby won't allow the
same class to be defined twice, so calling this helper function again
breaks things.

This commit removes the helper function call from the
cohdistributedscheme type.