builtin/remote: fix various trivial memory leaks

There are multiple trivial memory leaks in git-remote(1). Fix those.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t5514-fetch-multiple.sh

@@ -5,6 +5,7 @@ test_description='fetch --all works correctly'
 GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME=main
 export GIT_TEST_DEFAULT_INITIAL_BRANCH_NAME
 
+TEST_PASSES_SANITIZE_LEAK=true
 . ./test-lib.sh
 
 setup_repository () {