Improve test coverage for HTTP header.
Improve test coverage for HTTP header.

ossrs/srs,winlinvip/srs,ossrs/srs,winlinvip/srs,ossrs/srs,winlinvip/srs,winlinvip/simple-rtmp-server,winlinvip/srs,winlinvip/srs,ossrs/srs,ossrs/srs,winlinvip/srs,ossrs/srs