[bugfix] [RHEL/7] Update RHEL-7 service_*_enabled.sh remediation fixes to start using # systemctl ... rather than # chkconfig ...

Similarly like in previous service_*_disabled.sh remediation fixes case (which got actually merged already), update also the RHEL/7 service_*_enabled.sh remediation fixes to start using ```# systemctl enable / start service_name``` commands rather than / instead of their RHEL-6 ```# chkconfig --level 0..6 service_name on | chkconfig start service_name``` alternative which wouldn't work on RHEL-7.

Testing status:
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All of the changes have been first manually tested on RHEL-7 Server system for their proper work prior inclusion of the particular remediation fix change.

Please review.

Thanks, Jan.