cve-log: one 'stable' fix can point to several upstream commits

See 143d9963df6580491f9a5c38c9d4883786f78123
cve-log: fix -n<num> option

this was broken by commit 6b75f4f90ef4ac89598940eb53e0e880666dbee7

Signed-off-by: Franck Bui-Huu <fbuihuu@gmail.com>