remote-helpers: fix the run of all tests

We don't need to check for duplicate test numbers, we don't have them,
and either way test-lint-duplicates doesn't work in this situation.

Also, while we are on it, enable test-lint-shell-syntax to check for sh
errors.

Signed-off-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/remote-helpers/Makefile

@@ -3,6 +3,7 @@ TESTS := $(wildcard test*.sh)
 export T := $(addprefix $(CURDIR)/,$(TESTS))
 export MAKE := $(MAKE) -e
 export PATH := $(CURDIR):$(PATH)
+export TEST_LINT := test-lint-executable test-lint-shell-syntax
 
 test:
 	$(MAKE) -C ../../t $@