## Description of problem:

lvm no longer seems to report current information (lvmetad?)

## Version-Release number of selected component (if applicable):

rhv-h4.0 (rhvh-4.0-0.20160919.0)
vdsm-4.18.13-1.el7ev.x86_64
sos-3.2-35.el7_2.3.noarch

## How reproducible:

Always

## Steps to Reproduce:

1. check lvs output on SPM
2. create a new disk for a VM
3. check lvm output on SPM again

## Actual results:

It's there, but you can't see it (lvm commands).   Once 'pvscan --cache' is run, then the new lv can be 'seen'

## Expected results:

While this behaviour might be fine, we would at least like the vdsm plugin (sos) to run 'pvscan --cache' before collecting information.  There's a lot of information in this output (lvm size, tags, etc) that we can't easily get anywhere else, and it's critical for provide support for customers.

Asking customers to run 'pvscan --cache' on hosts before running LogCollector would not be acceptable.  

## Additional info: