Fix ipv6 bridge lines
The bridgeline generation was missing the "Bridge " prefix for ipv6 bridge lines, resulting in warnings like:
tor version Tor 0.4.9.0-alpha-dev (git-a56350abc8a8c18b) does not support: [::1]:5104 3701EBA8B358C71A3D85E56F0F4F89994BFEF209
and the line being commented out in the generated torrc.