Compare host and server name only once per call
Compare host and server name only once per call

The host name and the server name are not changed inside `#call(env)`,
so there is no need to compare them every time a mapping is tested.

Eric-Guo/rack,gioele/rack,imtayadeway/rack,gfvcastro/rack,Eric-Guo/rack,imtayadeway/rack,ngpestelos/rack,Eric-Guo/rack,wjordan/rack,imtayadeway/rack,gfvcastro/rack,gioele/rack,wjordan/rack,ngpestelos/rack,gfvcastro/rack,wjordan/rack,ngpestelos/rack,gioele/rack