Remove environment variable passing to remote tasks

This commit adds a utility method to send the build parameters to a
remote host and return the path on the remote filesystem as a string.
This method is then used in the remote tasks to determine various
parameters required for the build. This gets us out of the business of
passing along environment variables to the remote tasks, a source of
much pain as the remote tasks have become more complex.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>