Improve test coverage for config.
Improve test coverage for config.

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