b6b238a fixed the SLES4SAP detection, which was at this time ok.
Sadly Suse changed with SLES 15 the /etc/os-release file, so the above
change will no longer work.
This commit updates the SLES4SAP detection regarding
https://www.suse.com/support/kb/doc/?id=000019341.
The symlink realpath is matched with endswith, because in SLES 12+ the
link target is SLES_SAP.prod, but in SLES 11 the link target is
SUSE_SLES_SAP.prod.
(cherry picked from commit ea119d3089)
