lvm2: add lvm.con to CONFFILES

* Files will be over written when updating using rpm.

* If there is no %config micro before the file in the spec file,
  this file will be over-written after updating this package
  using rpm. This will make our settings lost.

Signed-off-by: Jian Liu <jian.liu@windriver.com>
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>