Grunt watch should not always run karma:server:run

currently grunt watch runs karma:server:run whenever a js file
changes even if karma is not running, or even worse,
when you've chosen to run karma separately via karma start.

This change has grunt watch run the karma:server:run task when
running the grunt autotest task only

/cc @eastridge
Merge pull request #115 from walmartlabs/grunt-watch-karma-server-run

Grunt watch should not always run karma:server:run