Nyx: empty exit policy if ipv6 address is not surrounded by [..]

./run_nyx

gives an empty

	exit policy:

line in that case. Example for a wrong line:

ExitPolicy reject6 <snip>/32

Good is

	ExitPolicy reject6 [<snip>]/32

Tested with latest stem and nyx Git trees.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information