09f5e97 ("travis-ci: skip a branch build if equal tag is present",
2017-09-17) introduced the "skip_branch_tip_with_tag" function with
a broken string comparison. Fix it!
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Lars Schneider <larsxschneider@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>