run-tests: rename test description dict to testdesc Previously the word "test" was used for both a Test instance and a path or test dict. This patch renames them so it's clear that "testdesc" is the dict, and "test" is the instance.

run-tests: change test identity from a path to a dict Previously, we use path to identify a test. A later patch adds more information so a path is not enough to identify a test. So we change it to a dictionary.

largefiles: delete unnecessary meddling with matcher internals lfutil.getstandinmatcher() was setting match._always to False because it wanted a matcher of no patterns to match no files and match.match() instead matches everything. However, since ba8089433090 (largefiles: ensure lfutil.getstandinmatcher() only matches standins, 2015-08-12), it never actually passes an empty list of patterns, so the hack has become unnecessary.