pylib: add support for disabling RCS in <file> tags

This commit add an attribute to the tag <file> which can be used
to disable revisioning of the file.

E.g.: it can be usefull for file inside /etc/modprobe.d/
pylib: use new method to access attribute in rocks.clusterdb

refactored some code to remove attribute access with
old style sql

- 40 line  of code :-)

 4 files changed, 25 insertions(+), 66 deletions(-)
tests: improvement to kickstart tests

and various fixes all over the place