Low: libcrmservice: Additional metadata fix for systemd templates.

A previous patch for this did not handle the possibility of templates
used with a unit file suffix. For example, chrony-dnssrv@ would work
but chrony-dnssrv@.template would not.

This patch takes care of the extra case. Additionally, it uses the
"pacemaker" instance name for both cases.

See: rhbz#2045096