bgpd: Drop unnecessary null-termination for fqdn

bgpd: Drop unnecessary null-termination for fqdn

str[len] is already null terminated before:

```
		if (len > BGP_MAX_HOSTNAME) {
			memcpy(&str, data, BGP_MAX_HOSTNAME);
			str[BGP_MAX_HOSTNAME] = '\0';
		} else if (len) {
			memcpy(&str, data, len);
			str[len] = '\0';
		}
```

CID: 1569357

Signed-off-by: Donatas Abraitis <donatas@opensourcerouting.org>