shellcheck: test_rebind.sh issues

In test_rebind.sh line 18:
clean () { test -n "$tmpdir" && test -d "$tmpdir" && rm -rf "$tmpdir" || :; }
                                                  ^-- SC2015: Note that A && B || C is not if-then-else. C may run when A is true.


In test_rebind.sh line 21:
tmpdir="`mktemp -d -t tor_rebind_test.XXXXXX`"
        ^-- SC2006: Use $(..) instead of legacy `..`.