INET_DIAG: Fix inet_diag_lock_handler error path. Upstream commit: 8cf8e5a67fb07f583aac94482ba51a7930dab493 Fixes:http://bugzilla.kernel.org/show_bug.cgi?id=9825The inet_diag_lock_handler function uses ERR_PTR to encode errors but its callers were testing against NULL. This only happen...