LP1865564 Holds grid avoid dupes (AngularJS)

LP1865564 Holds grid avoid dupes (AngularJS)

Address a couple if cases where the record holds grid in the AngularJS
staff catalog would make multiple network calls to fetch holds data.
In some cases, these calls would result displaying duplicate holds.

1. Avoid fetching holds when the pickup lib selector fires its on change
if the value provided matches the pickup lib we are already using.

2. Avoid reseting and reloading the grid during an active grid load.
Instead wait for the current load to complete before launching the next
load action.

Patch also includes a minor sanity check in the holdings code to avoid
console errors caused during pickup lib change.

Signed-off-by: Bill Erickson <berickxx@gmail.com>
Signed-off-by: Michele Morgan <mmorgan@noblenet.org>
Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>