t: switch "branch -l" to "branch --create-reflog"

t: switch "branch -l" to "branch --create-reflog"

In preparation for deprecating "-l", let's make sure we're
using the recommended option ourselves.

This patch just mechanically converts "branch -l" to "branch
--create-reflog".  Note that with the exception of the
actual "--create-reflog" test, we could actually remove "-l"
entirely from most of these callers. That's because these
days core.logallrefupdates defaults to true in a non-bare
repository.

I've left them in place, though, since they serve to
document the expectation of the test, even if they are
technically noops.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>