We were treating a url with a trailing slash differently than one
without. This CL treats them the same.
Additionally this fixes a bug in the way we iteratively try different
prefixes. We were only trying the host url but this change now tries all
different prefixes.
Fixes: #71889
Change-Id: I5d5f43000ae0e18ea8682050037253aff75ec142
Reviewed-on: https://go-review.googlesource.com/c/go/+/662435 Reviewed-by: Michael Matloob <matloob@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Sam Thanawalla <samthanawalla@google.com>