This converts the client and weldrcheck functions to use http.Client for
connections instead of passing around the socket path and opening it for
each test.
Currently the responses are all embedded in the weldr API functions.
They need to be usable by the client helper functions so I'm copying
them here and giving them names.
A later commit will go through the API can refactor it to use these
instead of the embedded ones.
This package will contain functions for communicating with the API that
can be used in both the integration tests as well as in a future cmdline
tool similar to composer-cli
When possible the client functions will return the same structures used
by weldr/api.go which have been exported in weldr/json.go
