integrate sles legacy init-script support

[floerica]

added a depending package (insserv-compat) to avoid strange errors on a fresh sles installation (/etc/init.d/.. not found)

[CLAassistant]

All committers have signed the CLA.

[floerica]

as requested in #172 - here is the PR

[ishanjainn]

LGTM! cc @gardar

[floerica]

for whatever reason my next patch got integrated into here - this was not really intended - i guess it happened as i wanted to have my merge request into my main fork.. However here are the informations:

• i added a few tasks in install.yml to prepare and update zypper
• tested this on openSuSE Leap - works perfektly fine on a fresh installed system
• tried to test on SLES15SP5 - but as my sles15sp5 is not registred within SuSe for proxy/firewall reasons, the grafana rpm install failes currently as some dependencies you can only get from SuSE Packagehub (firewall restrictions on my end) are not met
• if i install the 2 dependent packages (freetype, libttf) manually, then the role and installation goes through as expected

If you have concerns adding both patches at the same time, feel free to close my PR and i will open 2 seperate ones to integrate this stuff

[ishanjainn]

@gardar on this too, Thanks!