bus: Don't crash if inotify fails, even under DBUS_FATAL_WARNINGS=1
When running tests, we use DBUS_FATAL_WARNINGS=1 to make the tests fail on internal errors. Failing to set up inotify is not really an internal error: it's more like an environmental error, which can occur for reasons outside our control.
Instead, log using bus_context_log(), which never crashes the process and always just logs a warning.
Resolves: #473 (closed)