add fix_auth --v2 to fix bad/changed v2_keys

If a user wants to secure a manageiq appliance with a preshipped v2_key, they will need to fix any data already in the database. Even a blank database has a token in there.

Currently, `fix_auth.rb` will not clear out passwords encrypted with a lost `v2_key`. This code allows the admin to clear out those values and access the 

- don’t hardcode session token (pick a random one instead)

https://bugzilla.redhat.com/show_bug.cgi?id=1148590
@kbrock finds v2...?