fix sles bug (analogue to rhel)

[floerica]

Hello,

i tried to install grafana on a fresh installed sles box. It fails because of some systemv issues.
for rhel you have already a fix, i patched the same in the suse part. During my installation journey i might add other patches for sles too

file: roles/grafana/vars/distro/suse.yml

---
grafana_package: "grafana{{ (grafana_version != 'latest') | ternary('-' ~ grafana_version, '') }}"
# https://unix.stackexchange.com/questions/534463/cant-enable-grafana-on-boot-in-fedora-because-systemd-sysv-install-missing
# applies to SuSe too
_grafana_dependencies:
  - insserv-compat

[ishanjainn]

cc @gardar

[gardar]

@floerica could you open a PR?

[floerica]

done