Do not let cron fail on errors around prctl

wcs/qommon/cron.py

@@ -84,8 +84,15 @@ def spawn_cron(create_publisher):
         pub = create_publisher()
         # set process name, this only works on Linux, 15 == PR_SET_NAME
         if dl:
-            libc = dl.open('/lib/libc.so.6')
-            libc.call('prctl', 15, os.path.basename(sys.argv[0]) + ' [cron]\0', 0, 0, 0)
+            try:
+                libc = dl.open('/lib/libc.so.6')
+            except dl.error:
+                pass
+            else:
+                try:
+                    libc.call('prctl', 15, os.path.basename(sys.argv[0]) + ' [cron]\0', 0, 0, 0)
+                except ValueError: # missing symbol
+                    pass
         signal.signal(signal.SIGTERM, stop_cron_process)
         cron(pub)
         sys.exit(0)