Add malware domains list mirrors to sitescripts configuration

[kvas]

In order for the malware domains lists conversion script to use the mirrors (see #3774) the list of the mirrors should be added to sitescripts configuration file (see ​review for an example).

Without the configuration changes the script can still work in its currently proposed form with the hardcoded default list of mirrors. If the configuration changes are deployed to the servers before the changes are applied to the script the hardcoding doesn't need to be introduced, which would be preferable.

Thank you

[kvas]

The list of mirrors to add is the same as in the example in the review:

malwaredomains_mirrors=
	http://mirror3.malwaredomains.com
	http://mirror1.malwaredomains.com
	http://mirror2.malwaredomains.com

[abpbot]

A commit referencing this issue has landed:
​https://hg.adblockplus.org/infrastructure/rev/6eadff29bb96