[System.Net.Http] Use '*' as the host instead of '+' in the tests. Fixes xamarin/maccore#673.
Use '*' as the host instead of '+' in the tests.
The behavior should be the same, just faster, because '+' will fail to resolve
("Could not resolve host '+'"), and we'll fall back to the same behavior as
'*': https://github.com/mono/mono/blob/
5128cce2dcd097aa4e7b86dd3b56e833c15a9ff0/mcs/class/System/System.Net/EndPointManager.cs#L83-L96
The problem arises when failing to resolve '+' takes a long time: on some of
our bots it takes 5-10 seconds. This adds up quickly since the tests try many
times, effectively increasing a test run from 1-2 seconds to 30+ minutes.
Fixes https://github.com/xamarin/maccore/issues/673.