test-runner: don't fatally exit on bad test configuration

If a test has no hw.conf file test-runner was fully exiting and not
running any additional tests. This shouldn't happen in practice
since all upstreamed tests should run, but if any locally created
tests existed like this, it would cause the entire test run to exit
early.

Instead raise an exception which bails out of only that test, and
allows the rest to continue.

tools/test-runner

@@ -1072,8 +1072,7 @@ def pre_test(ctx, test, copied):
 
 	dbg("Starting test %s" % test)
 	if not os.path.exists(test + '/hw.conf'):
-		print("No hw.conf found for %s" % test)
-		exit()
+		raise Exception("No hw.conf found for %s" % test)
 
 	ctx.hw_config = ConfigParser()
 	ctx.hw_config.read(test + '/hw.conf')