in_http: Allow specifying the wildcard '*' as the CORS domain

[fujimotos]

This allows users to set up the configuration like below:

<match debug.**>
  @type http
  cors_allow_origins ["*"]
</match>

In this case, any origin can make a request to Fluentd; Plugin users
do not need to enumerate all the possible origins explicitly, so it
should be useful for, say, collecting data from a group of websites.

See MCD "Access-Control-Allow-Origin" header

Signed-off-by: Fujimoto Seiji [email protected]

[repeatedly]

Thanks!