dhcpv4: fix do_page_fault() when interface lost carrier

[updatede]

This fix issue #371 . According to avl.h, av_delete can’t be called in remove all elements loop.

[systemcrash]

ping @Alphix and @Noltari. WDYT?

[Noltari]

@updatede please fix the commit title
As reported at https://github.com/openwrt/odhcpd/actions/runs/21016348202/job/60422128645?pr=372, it should be something like:
dhcpv4: fix do_page_fault() when interface lost carrier

[systemcrash]

@updatede commit title, not PR title (needs force push) :)

[systemcrash]

merge commits are not accepted... just rebase on master if you must

[Alphix]

Hm, I could just do a quick check on my phone (not very ergonomic), I assume you want to fix the issue with:

bool dhcpv4_setup_interface()
   ...
   avl_remove_all_elements(...)
       dhcpv4_free_lease(...)

But dhcpv4_free_lease() is called from a bunch of other places, have you checked all callers? It seems likely that we'd end up free'ing but not removing leases in some cases. Wouldn't changing avl_remove_all_elements() to avl_for_each_element_safe() be a better option?

[updatede]

no, I haven’t check any other place where free something twice with av_delete, maybe triple , quadruple :) no I haven’t check it. Feel free to provide better solution.