git-cvsexportcommit.perl: exit with non-0 status if patch fails.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-cvsexportcommit.perl

@@ -190,7 +190,7 @@
     print "NOTE: One or more hunks failed to apply cleanly.\n";
     print "Resolve the conflicts and then commit using:n";
     print "\n    $cmd\n\n";
-    exit;
+    exit(1);
 }