Single thread dns query overwrite dns results for each nameserver

[lianke123321]

DNS result for one URL only has one dict for one nameserver because of this. It should be a list of dicts for each nameserver.

We should also be able to rule out non-related DNS servers. One way I figure is to get a local list of DNS servers before connecting to VPN, then remove any nameserver that is in the local list from the nameserver list after connecting to VPN. This should be done in centinel/vpn/cli.py

This bug also affects other repos. iclab-dmp, centinel-new-webinterface have to change.

[lianke123321]

Fixed