Add LF before missing contributor agreement error

This forces the text to start on the next line, so that the client
side added "remote: error: " prefix does not cause an incorrect
line wrapping of the message.

Change-Id: I11d1b154a6f55550a71dc35315fe62efa5a9a263
diff --git a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/ProjectServlet.java b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/ProjectServlet.java
index aa74485..df2c5c9 100644
--- a/gerrit-httpd/src/main/java/com/google/gerrit/httpd/ProjectServlet.java
+++ b/gerrit-httpd/src/main/java/com/google/gerrit/httpd/ProjectServlet.java
@@ -315,7 +315,7 @@
       if (s != Capable.OK) {
         GitSmartHttpTools.sendError((HttpServletRequest) request,
             (HttpServletResponse) response, HttpServletResponse.SC_FORBIDDEN,
-            s.getMessage());
+            "\n" + s.getMessage());
         return;
       }