Comment 1 for bug 1837067

Branch here: user/sandbergja/lp1837067_race_condition_in_replace_barcode
Here's a link: https://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/sandbergja/lp1837067_race_condition_in_replace_barcode

Testing instructions and other details from the commit message:

    To test:
    1) In the experimental Angular staff catalog, open up a bib record.
    2) Open the Holdings View tab.
    3) Select several items.
    4) Use the Actions for Selected Rows menu to Replace Barcodes
    5) Change the first barcode to something recognizable. Click the
    Replace Barcode button.
    6) Note that the dialog opens again to ask you to replace the
    barcode you just added.
    7) Apply this patch.
    8) Repeat steps 1-5.
    9) Note that the dialog opens again to ask you to replace the next
    barcode.

    Also removes some unused imports, and consolidates two RxJS pipes that were next to one another.