Serve 403 from RepositoryFilter on ServiceMayNotContinueException

This has no effect on Git clients, but for browsers, 403 Forbidden may
be more appropriate. 500 Internal Server Error implies that there is
a problem with the server, whereas ServiceMayNotContinueException is
specifically intended to cover cases where the server is functioning
correctly but has determined that the request may not proceed.

Change-Id: I825abd2a029d372060103655eabf488a0547c1e8

org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/RepositoryFilter.java

@@ -143,7 +143,7 @@ public class RepositoryFilter implements Filter {
 			res.sendError(SC_UNAUTHORIZED);
 			return;
 		} catch (ServiceMayNotContinueException e) {
-			sendError(req, res, SC_INTERNAL_SERVER_ERROR, e.getMessage());
+			sendError(req, res, SC_FORBIDDEN, e.getMessage());
 			return;
 		}
 		try {