Reset ping failures after any response

Use a fixed ping handler rather than scheduling a ping handler per ping
request.

If the XMPP client or server is busy, many outstanding ping requests
can be waiting, resulting in a number of ping handlers being queued.
Each of the ping handlers does the same thing (resets the failure count
to 0) but any dropped pings resulted in the handlers being queued
forever.

src/xmppipe.c

@@ -33,6 +33,7 @@ int handle_message(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
 int handle_presence(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
 int handle_presence_error(xmpp_conn_t * const, xmpp_stanza_t * const,
         void * const);
+int handle_ping_reply(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
 int handle_sm_request(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
 int handle_sm_enabled(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
 int handle_sm_ack(xmpp_conn_t * const, xmpp_stanza_t * const, void * const);
@@ -298,6 +299,7 @@ xmppipe_muc_init(xmppipe_state_t *state)
     xmpp_handler_add(state->conn, handle_version,
             "jabber:iq:version", "iq", NULL, state);
     xmpp_handler_add(state->conn, handle_message, NULL, "message", NULL, state);
+    xmpp_id_handler_add(state->conn, handle_ping_reply, "c2s1", state);
 
     /* Discover the MUC service */
     if (!state->out) {
@@ -978,7 +980,7 @@ handle_ping_reply(xmpp_conn_t * const conn, xmpp_stanza_t * const stanza,
 {
     xmppipe_state_t *state = userdata;
     state->keepalive_fail = 0;
-    return 0;
+    return 1;
 }
 
     void
@@ -1119,7 +1121,6 @@ xmppipe_ping(xmppipe_state_t *state)
     (void)xmpp_stanza_release(iq);
 
     state->keepalive_fail++;
-    xmpp_id_handler_add(state->conn, handle_ping_reply, "c2s1", state);
 }
 
     void