Update policy proto path for browser tests

This moved from policy/proto to components/policy/proto in https://codereview.chromium.org/2273783002 and this updates the Python server code to unbreak the test.

TBR=jianli@chromium.org

Review-Url: https://codereview.chromium.org/2286473003
Cr-Commit-Position: refs/heads/master@{#414628}

chrome/browser/policy/test/local_policy_test_server.cc

@@ -197,6 +197,7 @@ bool LocalPolicyTestServer::SetPythonPath() const {
   }
 
   AppendToPythonPath(pyproto_dir
+                     .AppendASCII("components")
                      .AppendASCII("policy")
                      .AppendASCII("proto"));
 #if defined(OS_CHROMEOS)