fs: Don't use ovirtfunctions for persistence

Previously the legacy ovirtfunctions module was used for the peristence
of files, on el7 this lead to problems.
Now the legacy module is not used anymore to prevent failing
persistence.

Change-Id: I19931fb98a113dba609ce484ec2f5031fd1f6936
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1152873
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>