virsh: volume: Fix lookup of volumes to provide better error messages
virsh: volume: Fix lookup of volumes to provide better error messages

If a user specifies the pool explicitly, we should make sure to point
out that it's inactive instead of falling back to lookup by key/path and
failing at the end. Also if the pool isn't found there's no use in
continuing the lookup.

This changes the error in case the user-selected pool is inactive from:

 $ virsh vol-upload --pool inactivepool --vol somevolname volcontents
 error: failed to get vol 'somevolname'
 error: Storage volume not found: no storage vol with matching path
 somevolname

To a more descriptive:

 $ virsh vol-upload --pool inactivepool --vol somevolname volcontents
 error: pool 'inactivepool' is not active

And in case a user specifies an invalid pool from:

 $ virsh vol-upload --pool invalidpool --vol somevolname volcontents
 error: failed to get pool 'invalidpool'
 error: failed to get vol 'somevolname', specifying --pool might help
 error: Storage volume not found: no storage vol with matching path somevolname

To something less confusing:

 $ virsh vol-upload --pool invalidpool --vol somevolname volcontents
 error: failed to get pool 'invalidpool'
 error: Storage pool not found: no storage pool with matching name 'invalidpool'

fabianfreyer/libvirt,libvirt/libvirt,datto/libvirt,datto/libvirt,zippy2/libvirt,crobinso/libvirt,datto/libvirt,shugaoye/libvirt,jardasgit/libvirt,nertpinx/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,agx/libvirt,agx/libvirt,zippy2/libvirt,agx/libvirt,olafhering/libvirt,crobinso/libvirt,elmarco/libvirt,VenkatDatta/libvirt,andreabolognani/libvirt,jardasgit/libvirt,VenkatDatta/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,jfehlig/libvirt,andreabolognani/libvirt,elmarco/libvirt,andreabolognani/libvirt,nertpinx/libvirt,shugaoye/libvirt,rlaager/libvirt,andreabolognani/libvirt,olafhering/libvirt,taget/libvirt,nertpinx/libvirt,rlaager/libvirt,VenkatDatta/libvirt,taget/libvirt,VenkatDatta/libvirt,elmarco/libvirt,eskultety/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,nertpinx/libvirt,VenkatDatta/libvirt,rlaager/libvirt,eskultety/libvirt,eskultety/libvirt,datto/libvirt,rlaager/libvirt,olafhering/libvirt,jardasgit/libvirt,eskultety/libvirt,shugaoye/libvirt,datto/libvirt,jardasgit/libvirt,libvirt/libvirt,libvirt/libvirt,taget/libvirt,elmarco/libvirt,fabianfreyer/libvirt,taget/libvirt,eskultety/libvirt,crobinso/libvirt,zippy2/libvirt,andreabolognani/libvirt,crobinso/libvirt,rlaager/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,taget/libvirt,agx/libvirt,jardasgit/libvirt,shugaoye/libvirt,elmarco/libvirt,agx/libvirt