lp1261835 stop colliding bill UI refreshes

lp1261835 stop colliding bill UI refreshes

for want of promises in Angular :)

population of the bill list in this implementation is asynchronous, but the rest
of the refresh action is not, and it's sadly being invoked multiple times. There
are different ways to fix this, but using a semaphore seems to work.

Signed-off-by: Jason Etheridge <jason@esilibrary.com>
Signed-off-by: Dawn Dale <ddale@georgialibraries.org>
Signed-off-by: Kathy Lussier <klussier@masslnc.org>