Fix repo-config set-multivar error return path.
Fix repo-config set-multivar error return path.

This hopefully fixes the problem an earlier commit 5d8ee9ceb attemted
to fix.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git