run-tests: make sure no_proxy/NO_PROXY are empty to fix test-http-proxy.t If no_proxy (or NO_PROXY) includes localhost, the test for detecting an unreachable proxy fails, because the proxy setting is ignored.

largefiles: test "lfconvert --to-normal" with rename/remove/merge This gets us very close to full test coverage of lfconvert. The only features not tested are: - .hgtags conversion - abort when largefile becomes symlink