only support openSUSE Leap 15.x, fail on 42.x

only support openSUSE Leap 15.x, fail on 42.x

openSUSE switched from 'openSUSE 13.x' to 'openSUSE Leap 42.x' and then to
'openSUSE Leap 15.x' to align with SLES15 development.
The previous logic did not correctly allow the current release, as 15.x matched
the 'less than 42.3' condition.

For now only support openSUSE Leap 15.x, and extend support once 16.x is
released (or whatever the exact version will be)

Signed-off-by: Johannes Kastl <kastl@b1-systems.de>
(cherry picked from commit 5ee3d96fb428a734c58d8823daf660b47595bafa)