zebra: fix double clearing of zif->es_info.es

zebra: fix double clearing of zif->es_info.es

This problem was accidentally introduced as a part of another fixup -
[
commit e378f5020d1af1aee587659e5602ee8c07eb05f4 (anuradhak/mh-misc-fixes, mh-misc-fixes)
Author: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>
Date:   Tue Sep 15 16:50:14 2020 -0700

    zebra: fix use of freed es during zebra shutdown
]

zif->es_info.es is cleared as a part of zebra_evpn_es_local_info_clear so it
cannot be passed around as a pointer from zebra_evpn_local_es_update/del.

Because of this bug removing ES from an interface resulted in
a zebra crash.

Signed-off-by: Anuradha Karuppiah <anuradhak@cumulusnetworks.com>