xenserver-firstboot update issue: firstboot_in_progress reappears

The xenserver-firstboot package adds the firstboot_in_progress flag file back when it is updated.

To reproduce:

• install XenServer 7.5
• on another similar computer or VM, install XenServer 7.4 then update it to 7.5 using the update ISO (not doing a full upgrade with the installation ISO)
• compare both: on XS 7.4 updated to XS 7.5, the /etc/firstboot.d/data/firstboot_in_progress file came back and subsequent reboots will not make it disappear.

If my understanding is correct, firstboot_in_progress should not come back. Or, if it should, then it should be removed on the next reboot.

I've made changes to the spec file to avoid that. The idea is that since the firstboot_in_progress is a volatile file, it should not belong to the xenserver-firstboot package. Otherwise it will be added back everytime it is updated. Instead, I install a copy of that file in %_datadir/xenserver-firstboot and copy it from there in %post, only during the initial installation of the xenserver-firstboot RPM.

Proposed patch: https://github.com/xcp-ng-rpms/xenserver-firstboot/commit/db642c8dc0727681a2012d788d07858d27286d8d

Does my patch seem to fix the issue in the proper way?