Use DefaultRenderer in TestGitilesServlet

This uses resources from the classpath for loading Soy template files,
which is appropriate behavior for tests. Unfortunately it does slow
down servlet setup in each test method slightly, as all the templates
need to be parsed. If this becomes an issue we can switch to using a
single servlet per test class.

Change-Id: I4aa2448c7e7d438420e7301f2bcc5e97ef182fa9
1 file changed