lvmdbusd: Reduce unnecessary state refreshes

lvmdbusd: Reduce unnecessary state refreshes

When we use udev or have lvm call back into the dbus service when a
change occurs, even if that change originated from the dbus service
we end up refreshing the state of the system twice which is not
needed or wanted.  This change handles this case by removing any
pending refreshes in the worker queue if the state of the system
was just updated.

Signed-off-by: Tony Asleson <tasleson@redhat.com>