glog flags (-v, -logtostderr) are registered on weed's global flagset,
so passing them after the subcommand name kills the process at flag
parsing: flag provided but not defined: -logtostderr. The old stat-based
mount readiness probe masked this — TestWriteBufferCap silently ran
against the bare local directory and passed. The device-ID readiness
check now surfaces the dead mount as a not-ready timeout.
Move glog flags into MountGlobalOptions, emitted before the subcommand,
and do the same for the EnableDebug verbosity flag on mini and mount.