mme: fix missing memset in mme_fd_init

The 'data' struct used to specify the diameter dispatch options for the
MME callbacks was not being initialized properly, which meant that the
App id could contain garbage. This was preventing the callbacks from
being invoked when receiving ISD/CLR requests.

src/mme/mme-fd-path.c

@@ -2193,6 +2193,7 @@ int mme_fd_init(void)
     ogs_assert(ret == 0);
 
     /* Specific handler for Cancel-Location-Request */
+    memset(&data, 0, sizeof(data));
     data.command = ogs_diam_s6a_cmd_clr;
     ret = fd_disp_register(mme_ogs_diam_s6a_clr_cb, DISP_HOW_CC, &data, NULL,
                 &hdl_s6a_clr);