FBR: Fix the freezelist script

[Clement Verna]

Hi all,

I found out that the freezelist script did not work with ansible
2.7.10. Once the script changed to use the new api, it complained
about 2 non valid yaml file (error    syntax error: found character
'\t' that cannot start any token) in the vars. So I replaced the tabs
character by spaces.

See the attached patch +1s ?