add admin server type in runtime options

[wwbmmm]

Change-Id: Ie00658b19606c9238ee71c5ab66434481c22202d

We always use fastcgi server for compatibility, but we don't want the admin server to be fastcgi. It is not convenient to visit. So we add a patch to make admin server type different from page server type.

In Baidu, we always use fastcgi for page server and http for admin server.

Just add this in you ini setting: hhvm.admin_server.type=proxygen

If this is not set, the default value is the same type as the page server.

[hhvm-bot]

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