* Refactor integration test for lvg module to introduce grow/reduce test
* List correctly current PV in lvg module: fix lvg reduce
Previous behaviour was to only take into account PV passed in 'pvs'
argument. This lead to reduce not working as expecting:
* with state=present and list of wanted pvs, lvg found only the pvs to
add or already present and ignored the pv to remove (obviously absent
from the list of given PV)
* with state=absent and a pv to remove, lvg found that the remaining pvs
list is empty (ignoring possible other PV in the vg) and decides to
remove the vg entirely (as supposely no PV are left anymore to store
lvm metadata)
* Add changelog fragment
