wtp: rework kernel socket handling

Switch to a connected UDP kernel socket. Comparing the
local and remote IPs is no longer required and handling
different IP versions and UDP types is automatic.

The WTP logic needs to reopen the socket on demand now.

src/wtp/wtp.c

@@ -1229,12 +1229,6 @@ static int wtp_configure(void) {
 		return WTP_ERROR_NETWORK;
 	}
 
-	/* Bind data address */
-	if (wtp_kmod_bind(g_wtp.net.localaddr.ss.ss_family)) {
-		capwap_logging_fatal("Cannot bind data address");
-		return WTP_ERROR_NETWORK;
-	}
-
 	return CAPWAP_SUCCESSFUL;
 }