Changes

contrib/osmo-sgsn.spec: fix build for almalinux:8

Add the missing "%if 0%{?suse_version}" around %service_del/add
commands, as these are only available on opensuse.

Fixes: a07e6d9c (".deb/.rpm: add osmocom user during package install")
Change-Id: I89802f926bfccc0f7b4bb1ff64115b232b1db022