fix: prevent autoping disable on false negative ping support check

Remove autodisable logic (prefs_set_autoping(0)) and early return in autoping
to treat intermittent false negatives from connection_supports(XMPP_FEATURE_PING).
Add one-time error display with debug features print for monitoring; warn on first failing
check without aborting to maintain functionality while investigating root cause.

tests/unittests/xmpp/stub_xmpp.c

@@ -156,6 +156,11 @@ connection_get_profanity_identifier(void)
     return "profident";
 }
 
+void
+connection_debug_print_features()
+{
+}
+
 jabber_conn_status_t
 connection_register(const char* const altdomain, int port, const char* const tls_policy,
                     const char* const username, const char* const password)