Add a flag to set the hostname when running tests
Add a flag to set the hostname when running tests

For complex testing setups, the browser running the tests may need to
point to a hostname other than localhost.  This adds a flag that can
be used with build/test.py to set the hostname which is passed from
karma to the browser.

Change-Id: I66757d3d42a83e24c2edab9e211f75cb2745a284

TheModMaker/shaka-player,shaka-project/shaka-player,tvoli/shaka-player,TheModMaker/shaka-player,TheModMaker/shaka-player,russitto/shaka-player,brightcove/shaka-player,Ross-cz/shaka-player,russitto/shaka-player,TobbeEdgeware/shaka-player,tvoli/shaka-player,TobbeEdgeware/shaka-player,TobbeEdgeware/shaka-player,tvoli/shaka-player,TheModMaker/shaka-player,Ross-cz/shaka-player,russitto/shaka-player,brightcove/shaka-player,vimond/shaka-player,indiereign/shaka-player,indiereign/shaka-player,Ross-cz/shaka-player,vimond/shaka-player,brightcove/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,vimond/shaka-player,indiereign/shaka-player,tvoli/shaka-player,shaka-project/shaka-player