Web client: cannot edit item or call number after mono part assigned

I filed a new bug and found this one later. Here is more information to lead us to a solution:

When editing an existing copy that is already assigned a part using the web based staff client, we are seeing errors in the logs:

open-ils.cstore 2017-12-29 15:02:35 [ERR :734:oils_sql.c:2522:151455963470971582] open-ils.cstore ERROR inserting biblio::monograph_part object using query [INSERT INTO biblio.monograph_part (id,record,label,label_sortkey,deleted) VALUES (DEFAULT,1039176,'2017/11&/12',DEFAULT,DEFAULT);]: 3505685 3505685: ERROR: duplicate key value violates unique constraint "record_label_unique_idx"
DETAIL: Key (record, label)=(1039176, 2017/11&/12) already exists.

[2017-12-29 15:02:35] open-ils.cat [ERR :29061:CStoreEditor.pm:139:151455963470971582] editor[1|10497] request error open-ils.cstore.direct.biblio.monograph_part.create : <new object> : Exception: OpenSRF::DomainObject::oilsMethodException 2017-12-29T15:02:35 OpenILS::Utils::CStoreEditor /usr/local/share/perl/5.22.1/OpenILS/Utils/CStoreEditor.pm:465 <500> INSERT error -- please see the error log for more details

[2017-12-29 15:02:35] open-ils.cat [ERR :29061:EX.pm:66:151455963470971582] Exception: OpenSRF::DomainObject::oilsMethodException 2017-12-29T15:02:35 OpenILS::Utils::CStoreEditor /usr/local/share/perl/5.22.1/OpenILS/Utils/CStoreEditor.pm:478 <500> INSERT error -- please see the error log for more details

[2017-12-29 15:02:35] open-ils.cat [INFO:29061:CStoreEditor.pm:139:151455963470971582] editor[1|10497] request returned no data : open-ils.cstore.direct.biblio.monograph_part.create

It's attempting to create a new part when it needs to just use the one that it already has.

Something I've noticed in playing with the Chrome debugger:
It looks like $scope.updatePart is being called before the parts_list has been built which is why it keeps trying to create new parts; as far as the editor can tell at the time you're adding a new part and when the backend tries to create it on save everything falls down. Forcing the parts list to completely load before loading the item should make this just go away.

I have pushed a potential fix for this at
http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/dpearl/LP1739271_mono_part_error

I've had a couple people test Dan's branch and it works as expected. Signoff here: http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/jboyer/lp1739271_edit_items_with_parts_signoff

working/user/jboyer/lp1739271_edit_items_with_parts_signoff

Picked to master, rel_3_0, and rel_3_1. Thanks, Dan and Jason!