Make default test timeout to be 300 seconds to allow slow tests to pass on slow systems

systemd-248-increase_test_timeouts.patch

@@ -6,7 +6,7 @@ diff -uNr systemd-248/meson.build systemd-248-increase_test_timeouts/meson.build
          defs = tuple.length() > 6 ? tuple[6] : []
          parallel = tuple.length() > 7 ? tuple[7] : true
 -        timeout = 30
-+        timeout = 60
++        timeout = 300
  
          name = sources[0].split('/')[-1].split('.')[0]
          if type.startswith('timeout=')