Fix conduit host check

Summary:
conduit was using getProductionURI instead of getURI for checking that the
request was sent to the correct host, which causes problems in some dev
environments

Test Plan:

echo '{}' | arc call-conduit --conduit-uri=mydevserver

where my dev server is configured with phabricator.production-uri pointing to
prod instead of my devserver

Reviewers: epriestley, btrahan, jungejason

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1543