[subset] Do not compare ttx progress output in the tests

Suppress progress messages of ttx. This avoids comparing this output to the reference file which lets the test fail.

test/subset/run-tests.py

diff --git a/test/subset/run-tests.py b/test/subset/run-tests.py
index 0b119fe..1cd1a19 100755
--- a/test/subset/run-tests.py
+++ b/test/subset/run-tests.py
@@ -80,6 +80,7 @@
 def run_ttx(file):
 	print ("ttx %s" % file)
 	cli_args = ["ttx",
+		    "-q",
 		    "-o-",
 		    file]
 	return cmd(cli_args)