libvirt_configure.sh: Unpersist logrotate libvirt

Before commenting previous logrotate configuration in ovirt-node
we must unpersist the file. This patch moves the unpersist command
to few lines above. Only required for this branch since contains
legacy code, master and ovirt-3.5 branches contains new code.

Label: ovirt-3.4-only
Change-Id: I28880b8a73f1ddd9034eca494b7564019217bfe9
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1115997
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/29731
Reviewed-by: mooli tayer <mtayer@redhat.com>
Reviewed-by: Yaniv Bronhaim <ybronhei@redhat.com>