fix(instances): a disk on an LVM pool is not resized, the page says so instead of failing

libvirt's logical pool cannot change a volume's capacity, so every
resize of such a disk ended in a 500. Disks are resized one at a time;
VIR_ERR_NO_SUPPORT becomes a message naming the disk, and the other
disks still grow.

A live test creates an LVM pool from the storage page on a spare disk
(TEST_LIBVIRT_LVM_DEVICE; the Vagrant computes get /dev/vdb), attaches
new and existing volumes to stopped and running VMs as block disks, and
checks the refused resize in every state.

vrtManager/instance.py

@@ -1495,8 +1495,9 @@ class wvmInstance(wvmConnect):
 
     def resize_disk(self, disks):
         """Grow disks. QEMU holds the lock of a running domain's image files and
-        grows them itself; block volumes (e.g. LVM) are grown by the storage
-        pool first, then QEMU is told the new size."""
+        grows them itself; other volumes are grown by the storage pool first,
+        then QEMU is told the new size. A pool that cannot resize volumes (LVM
+        for one) raises VIR_ERR_NO_SUPPORT before anything changes."""
         active = self.instance.isActive()
         for disk in disks:
             vol = self.get_volume_by_path(disk["path"])