Display any errors from querying LVM2 PVs to the user (#160787)

Previously any errors which occurred when running LVM commands used to
load the LVM2_PV_Info cache were simply ignored and the cache wasn't
loaded.  This lead to missing information about LVM2 PVs, but the user
had no indication as to why.

Now when any errors occur the command ran and all output is captured.
This is displayed to the user, along with a suitable warning message, in
the Partition Information dialog.

Bug #160787 - lvm support