patch-iso fails on pxe-network-installer patch

[Don Penney]

Brief Description
-----------------
Running patch-iso with a pxe-network-installer patch fails, due to an older restructuring of pxe-network-installer when the grub2 package was upversioned in 2018. The pxe-network-installer spec and build-iso package were updated, but patch-iso was not:
https://opendev.org/starlingx/metal/commit/d58a4ca481e02d3e8aa952bd6251a99cd86986d0
https://opendev.org/starlingx/root/commit/3a37c7feed50cde3e2c5f619cb85c97a7c1b18d7

Extraction of pxe-network-installer files fails with:
cp: cannot stat ‘pxeboot/EFI/centos/x86_64-efi/*’: No such file or directory
Error: Could not copy all files from installer

Severity
--------
Minor

Steps to Reproduce
------------------
Create a pxe-network-installer patch and run patch-iso to add it to an ISO.

Reproducibility
---------------
Reproducible

Branch/Pull Time/Commit
-----------------------
master, as of Aug 20, 2020

Last Pass
---------
This appears to have been broken since 2018

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.opendev.org/747297

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/747297
Committed: https://git.openstack.org/cgit/starlingx/root/commit/?id=466ce2c528b6e9f72005053b261a4b023ead47b1
Submitter: Zuul
Branch: master

commit 466ce2c528b6e9f72005053b261a4b023ead47b1
Author: Don Penney <email address hidden>
Date: Thu Aug 20 17:52:54 2020 -0400

    Fix patch-iso pxe-network-installer handling

    Changes made previously to upversion grub2 in starlingx resulted in
    some restructuring of the pxe-network-installer package, and
    corresponding changes in build-iso. These changes were not reflected
    in patch-iso, however. This update fixes the handling of
    pxe-network-installer extraction, and includes additional grub2
    packages in the patch support.

    Change-Id: Ib72a44d2d5a39fe41023be8feb83b88e5f39435b
    Closes-Bug: 1892424
    Signed-off-by: Don Penney <email address hidden>