Make t9150 and t9151 test scripts executable

so that they can be run individually as
(cd t && ./t9150-svk-mergetickets.sh)
etc. just like all other test scripts.
Signed-off-by: NMichael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>