tests/qtest/fuzz: fix memleak in qos_fuzz.c

Found with fuzzing for qemu-8.2, but also relevant for master

Signed-off-by: Dmitry Frolov <frolov@swemel.ru>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alexander Bulekov <alxndr@bu.edu>
Message-ID: <20240521103106.119021-3-frolov@swemel.ru>
Signed-off-by: Thomas Huth <thuth@redhat.com>
diff --git a/tests/qtest/fuzz/qos_fuzz.c b/tests/qtest/fuzz/qos_fuzz.c
index b71e945..d3839bf 100644
--- a/tests/qtest/fuzz/qos_fuzz.c
+++ b/tests/qtest/fuzz/qos_fuzz.c
@@ -180,6 +180,7 @@
 
         fuzz_path_vec = path_vec;
     } else {
+        g_string_free(cmd_line, true);
         g_free(path_vec);
     }