Curl is an important package that we end up needing in a few places. To
avoid puppet unique name conflicts with the package "curl" only define
the curl package resource if it isn't already defined.
This allows us to define it in multiple places that may or may not
overlap depending on how hosts are constructed.
Change-Id: Icd0c652ff2f522ce2ea9086965f53e1a03f0d4fd
31e44bbcb0