When we use IPv6 address as Netflow server `uacctd` generates plugin name with "colons" `::`
Example VyOS configuration
```
set system flow-accounting interface 'eth0'
set system flow-accounting interface 'eth1'
set system flow-accounting netflow engine-id '100'
set system flow-accounting netflow sampling-rate '1'
set system flow-accounting netflow server 2001:db8::1 port '2055'
set system flow-accounting netflow source-ip 2001:db8::2
set system flow-accounting netflow timeout expiry-interval '60'
set system flow-accounting netflow version '9'
```
uacctd doesn't like this format:
```
root@r1:/home/vyos# pmacctd -f /etc/pmacct/uacctd.conf -i eth0
ERROR: [/etc/pmacct/uacctd.conf:14] Syntax error: illegal brackets. Exiting.
root@r1:/home/vyos#
```
Generated config:
```
root@r1:/home/vyos# cat /etc/pmacct/uacctd.conf
# Genereated from VyOS configuration
daemonize: true
promisc: false
pidfile: /var/run/uacctd.pid
uacctd_group: 2
uacctd_nl_size: 2097152
snaplen: 128
aggregate: in_iface,src_mac,dst_mac,vlan,src_host,dst_host,src_port,dst_port,proto,tos,flows
plugin_pipe_size: 10485760
plugin_buffer_size: 10485
imt_path: /tmp/uacctd.pipe
imt_mem_pools_number: 169
plugins: nfprobe[nf_2001:db8::1],memory
nfprobe_receiver[nf_2001:db8::1]: 2001:db8::1:2055 <== line 14
nfprobe_version[nf_2001:db8::1]: 9
nfprobe_engine[nf_2001:db8::1]: 100
sampling_rate[nf_2001:db8::1]: 1
nfprobe_source_ip[nf_2001:db8::1]: 2001:db8::2
nfprobe_timeouts[nf_2001:db8::1]: expint=60
```
To fix it we have to use `dash` or `underscore`
Also, it must use brackets
Wrong format:
```
nfprobe_receiver[nf_2001:db8::1]: 2001:db8::1:2055
```
Expected format:
```
nfprobe_receiver[nf_2001-db8--1]: [2001:db8::1]:2055
```