t6036: fix broken "merge fails but has appropriate contents" tests
These tests reference non-existent object "c" when they really mean to
be referencing "C", however, these errors went unnoticed due to a broken
&&-chain later in the tests. Fix these errors, as well as the broken
&&-chains behind which they hid.
Reviewed-by: Elijah Newren <newren@gmail.com> Signed-off-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>